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THE 



PRINCIPLES 



OF 



CHEMISTRY: 



PREPARED FOR THE USE OF 



SCHOOLS, ACADEMIES, AND COLLEGES. 



By DANIEL B. SMITH. 



SECOND EDITION, 

REVISED AND ADAPTED TO THE PRESENT CONDITION OF THE SCIENCE. 



PHILADELPHIA: 
URIAH HUNT, 101 MARKET STREET. 



Entered according to the act of Congress, in the year 1842, by Uriah Hunt, in 
the office of the Clerk of the District Court, of the Eastern District of Pennsyl- 






Printed by 

WILLIAM S. MARTIEN. 






CONTENTS 



Page 

A. 

Absorption of gases by solids, 131 

Acetates, . . 239 

Acetule, . . . 213, 237 

Acids, .... 117, 135 

Bibasic, . .188 

Monobasic, . .188 

Native organic, . 253 

Polybasic, . . 188 

Pyrogenous, • . 254 

Tribasic, . . .188 

Acid, Acetic, . . . 237 

Aconitic, . . . 254 

Arsenious, . . 161 

Aspartic, . . • 280 

Benzoic, . . 249 

Boracic, • . . 159 

Bromic, . . 140 

Bromohydric, . .181 

Camphoric, . . 247 

Carbazotic, . .279 

Carbonic, . . 222 

Chloracetic, . .213 

Chloric, ... 139 

Chlorohydric, . .179 

Chlorous, . . 138 

Choleic, . . .283 

Chromic, . . 163 

Citric, . . .256 

Croconic, . .226 

Cyanic, . . .265 

Cyanohydric, . 267 

Cyanuric, . . . 267 

Fluoborohydric, . 182 

Fluohydric, . . 181 

Fluosilicohydric, . 182 

Formic, . . .239 

Fulminic, . . 266 

Gallic, . . ,257 

Hy pochlorous, . 138 

Hyponitrous, . .154 



Acid, 



Hypophosphorous, 

Hyposulphuric, 

Hyposulphurous, 

Iodic, 

Iodohydric, 

Lactic, 

Malic, . 

Maleic, 

Mangarfic, 

Margaric, . 

Mellitic, 

Metagallic, 

Metaphosphoric, 

Mucic, 

Muriatic, 

Nitric, 

Nitrous, . 

Oleic, 

Osmic, . 

Oxalic, 

Pectic, . 

Perchloric, 

Periodic, 

Permanganic, 

Phosphoric, 

Phosphorous, 

Picric, . 

Pyrocitric, 

Pyrogallic, 

Pyroligneous, 

Pyrophosphoric, 

Racemic, . 

Rhodizonic, . 

Saccharic, . 

Selenic, . 

Selenious, . 

Selenohydric, 

Silicic, 

Stearic, . 

Sulphindylic, 

Sulphocarbonic, 



Page 

146 
. 144 

144 
. 140 

181 
. 241 

256 
. 256 

162 
. 252 

226 
. 258 

146 
. 216 

179 
. 155 

154 
. 252 

163 
. 221 

258 
. 140 

140 
. 162 

145 
.•145 

279 
. 254 

258 
. 238 

146 
. 255 

226 
. 232 

145 
. 144 

175 
. 160 

251 
. 278 

227 



4 CONTENTS. 






Page 




Page 


Acid, Sulphohydric, . 


172 


Atomic weights, table of, 1 1 ' ; 


Sulphopurpuric, 


278 


Attraction of cohesion 


, . 15 


Sulphovinic, 


234 


of gravitation, . 13 


Sulphuric, 


141 


Azote, 


. 82 


u hydrated, . 


142 


B. 




Sulphurous, . . 


140 


Balsams, 


. 249 


Tannic, • 


256 


Barium, . 


. 107 


Tartaric, • 


254 


Chloride of, , 


. 194 


Tartralic, . 


255 


Deutoxide of, 


. 168 


Uric, 


284 


Protoxide of, 


. 168 


Affinities, Divellent, . 


126 


Sulphuret of, 


. 173 


Quiescent, 


126 


Baryta, 


. 168 


Affinity, Chemical, 


124 


Bases, 


119, 135 


influenced by cohe- 




Bassorine, . 


. 231 


sion, . 


132 


Bell-metal, 


. 177 


" elasticity, 


132 


Benzule, 


212, 248 


Air, atmospheric, 


147 


Protoxide of, 


. 249 


Albumen, . . 259, 


260 


Benzamide, . 


. 273 


Alcohol, . . . 219, 


233 


Bile, 


. 283 


Wine, 


214 


Bismuth, 


. 101 


Wood, . 


214 


Blood, . 


. 281 


Aldehyde, 


213 


Bodies, isomorphous, 


. 191 


Alkalies, .... 


170 


Bones, 


. 264 


Alloys, .... 


177 


Borax, 


. 87 


Alumina, 


166 


Boron, 


87 


double sulphates of 


, 192 


Salts of, . 


. 206 


Aluminium, 


105 


British gum, . 


. 229 


Sesquioxide of, 


166 


Brass, .... 


. 177 


Sesquichlorideof 


, 195 


Bromides, 


. 198 


Amalgams, 


178 


Bromine, 


. 81 


Amide, 


269 


Bronze, . 


. 177 


Ammonia, 


270 


C. 




Carbonates of, 


275 


Cadmium, 


. 103 


double nature of, 


273 


Caffeine, 


. 280 


Ammonium, 


271 


Calcium, . 


. 107 


Protoxide of, 


271 


Chloride of, . 


. 194 


Amule, .... 


240 


Fluoride of, 


. 199 


Amygdaline, . 


249 


Protoxide of, 


. 169 


Anode, . . i 


71 


Phosphuret o: 


; . 175 


Anthracite, 


246 


Sulphuret of, . 


. 173 


Antimony, .... 


95 


Calomel, . 


. 196 


Chlorides of, . 


196 


Caloric, 


. 20 


Arabine, .... 


231 


Capacity for, 


29 


Aracina, .... 


276 


Transmission < 


>f, . 44 


Arsenic, .... 


94 


Calorimiter, 


29 


Sesquihydroguret 


176 


Camphene, . 


. 247 


Salts of, 


205 


Camphor, 


. 247 


Sulphurets of, 


179 


Artificial, 


. 248 


Asparagine, 


280 


Cane Sugar, 


. 231 





CONTENTS. 


5 




Page 




Page 


Canton's phosphorus, . 


. 173 


Copper, .... 


103 


Caoutchouc, 


248 


Oxides of, . 


164 


Caramel, 


. 232 


Sulphurets of, 


174 


Carbon, . 


85 


Corrosive sublimate, . 


196 


Bromide of, 


. 226 


Creasote, .... 


246 


Chlorides of 


226 


Cryophorus, 


36 


Iodides of, 


. 226 


Crystallization, 


15 


Carbonates, . . . 


224 


Cyanogen, . 


264 


Carbonic Oxide, . 


. 220 


Cyanides metallic, . 


267 


Caseine, . 


251 


D. 




Catalysis, . . . 


. 220 


Daguerreotype, the, 


56 


Cathode, . 


71 


Daniell's constant battery, . 


69 


Cast-iron, . 


. 104 


Decomposition electrolytic, 


121 


Cerasine, . 


231 


from molecular 




Cerium, 


. 105 


agitation, 


128 


Cetule, . 


240 


caused by the 




Chameleon mineral, . 


. 162 


presence of a 




Charcoal, 


86 


third body, . 


130 


Chemical union, force of 


. 128 


Definite proportions, law of, 


109 


Chlorates, 


202 


Dextrine, . 


233 


Chlorides, . 


. 194 


Diamond, 


85 


Chlorine, . 


78 


Diastase, . . . . 


232 


Peroxide, 


. 138 


E. 




Protoxide, . 


138 


Ebullition, . 


36 


Salts of, 


. 202 


Elective affinity, 


124 


Chrome, . 


95 


Double, 


125 


Salts of, 


, 206 


Simple, . 


125 


Chyle, . 


, 283 


Electricity, . . . . 


58 


Chyme, . . # 


. 283 


from friction, 


59 


Cinchonia, 


. 276 


Induction of, 


61 


Cinnamule, . 


. 249 


Theory of, 


61 


Coal, bituminous, . 


245 


from chemical 




Cobalt, 


. 105 


action, 


65 


Chloride of • 


, 195 


Electro-chemical decomposi- 




Cobaltocy anogen, 


. 269 


tion, theory of, 


70 


Colours of bodies, . 


56 


Electro-magnetism, 


72 


Colouring" matters, red, 


. 279 


Elements, proximate and ul- 




Columbium, 


97 


timate, . 


112 


Combination, on, 


. 108 


Equivalent numbers, 


110 


Change of p 


ro- 


Essential oils, 


246 


perties b] 


n . 126 


Ethal, . . . 214, 


241 


Heat and li 


?ht 


Ether sulphuric, . 


234 


extricated 


by, 127 


Eudiometry, 


150 


Change of c 


en- 


Expansion, . 


21 


sity in, 


. 133 


F. 




" of form 


in, 133 


Fecula, 


. 228 


" of colour 


in, 134 


Fermentation, vinous, 


233 


Compounds, bi-elementar 


y, 134 


Ferments, . 


. 218 


Cooling of bodies, law of, 
1* 


. 50 


Ferrocy anogen, 


269 



6 



CONTENTS. 



Ferridcyanogen, . 

Fibrine, .... 

Flame, . . . . 

Fluids, solvent power of, . 

Fluorides, . 

Fluorine, .... 

Forces, electrical and chemi- 
cal, identity of, 

Formule, . 

G. 

Galvanic battery, 

Galvanism, how developed, 

Galvanometer, 

Gases, absorption of, by so- 
lids, . 

Liquefaction of, 
Penetration of, 

Gastric juice, . 

Geine, 

Gelatine, . 

Glass, . 

Glucina, . 

Glucinium, . 

Glucose, . 

Gluten, 

Glycerine, 

Gold, 

Chlorides of, 

Graphite, 



Page 
269 
259 

43 
131 
199 

82 

124 
240 

68 
65 
72 



Indigo, 

Ink, sympathetic, 

Inuline, 

Iodides, 

Iodine, 

Iridium, 

Iron, . 

Chlorides of, 
Iodides of, 
Oxides of, 
Sulphurets of, 

Isomerism, 

Isomorphism, 



Gum, 
Gunpowder, 



H. 



131 

39 

. 40 
. 282 

. 242 
. 263 

. 207 
. 166 

. 106 
. 232 

. 260 
. 252 

. 98 
. 197 

. 86 
218, 228, 230 

. 202 



Kakodule, 



Haloid salts, . . 136, 193 

Hsematosine, . . . 282 
Heat, .... 20 

Capacity for, • . 29 
of fluidity, . .31 

Latent, ... 33 
Specific, , . .30 
Transmission of, . 44 
Homberg's pyrophorus, . 173 
Humus, .... 242 
Hydrogen, ... 83 
Peroxide of, . 158 

Light carburetted, 243 
History of Chemical Phi- 
losophy, .'••", .286 
I. 
Incandescence, . . 42 



K. 
L. 



Lactine, 
Lanthanium, . 
Latent heat, 
Law of cooling, 

of substitution, 
Lead, 

Chloride of, 

Iodides of, 

Oxides of, . 

Sulphuret of, 
Leyden jar, 
Light, . m . 

Refraction of, 

Reflection of, 

Decomposition ofj 

Calorific rays of, 

Chemical rays of, 
Lignine, 
Lime, 

Hypochlorite of, 

Sulphate of, 
Lithia, 
Lithium, 

Protoxide of, 
M. 
Magnesia, 
Magnesium, 

Protoxide of, 
Chloride of, 
Magnetism, 
Manganese, 

Chlorides of 
Perfluoride of, 



Page 
277 
195 
229 
198 
80 
100 
103 
195 
198 
165 
174 
112 
191 

215 

241 

105 

31 

50 

. 215 

102 

, 196 

198 

, 164 

174 

. 63 

52 

. 53 

53 

. 54 

55 

. 55 

228, 230 

169 



202 
200 
171 
107 
171 

169 
106 
169 
195 
58 
96 
195 
199 






CONTENTS. 



Page 
Mannite, . . .241 
Margarine, . . . 252 
Mellon, .... 269 
Mercury, . . . .101 
Bicyanide of, . 267 
Bisulphuret of, . 174 
Chlorides of, . 196 
Iodides of, . 198 
Oxides of, . .164 
Metals, . . . . 91 
Fulminating com- 
pounds of the, . 276 
Methule, ... 239 
Milk, . . . .282 
Molybdenum, . . . 96 
Sulphuret of, 174 
Mordants, . . . .279 
Morphia, ... 277 
Multiple proportions, law ofj 110 



Mucus, 



N. 



Naphthaline, 
Nickel, . 
Nitrogen, 

Protoxide of, 
Deutoxide of, 
Terchloride of, 
Salts of, 
Nomenclature, chemical, 

O. 
Oil of bitter almonds, 

of potato spirit, 
Oils, Animal, . 
Drying, 
Essential, ; 

Fixed, 
Oily acids, 

Oleine, • . . . 

Olefiant gas, 
Organic alkalies, • 

chemistry, 
radicals, 
products, spontane- 
ous change in, 
Osmium, . 
Oxamide, 
Oxides, the, 
Oxygen, 



282 

217 
100 
82 
151 
153 
275 
201 
117 

249 

214, 240 

. 250 

. 251 
. 246 

. 250 
. 250 

. 252 
. 236 

. 276 
. 209 

. 211 



217 

97 

273 

136 

77 



P. 



Page 



Palladium, 


. 99 


Paracyanogen, 


265 


Pectine, 


. 258 


Pepsine, 


283 


Piperine, 


. 281 


Phosphorescence, . « 


57 


Phosphorus, 


. 90 


Oxide of, 


145 


Sesquihydroguret of, 


. 175 


Salts of, 


203 


Plasters, 


. 251 


Platinum, 


99 


Porcelain, . 


. 208 


Potassa, . 


. 171 


Bitartrate of, 


; 254 


Chlorate of, 


203 


Nitrate of, , 


. 202 


Potassium, 


167 


Chloride of, 


. 194 


Cyanide of, 


. 267 


Oxide of, 


. 171 


Fluoride of, 


199 


Sulphuret of, 


. 173 


Prince Rupert's drops, 


129 


Proteine, 


. 262 


Prussian Blue, 


268 


Pyroxylic spirit, 


. 238 


Pyrometer, 


22 


Breguet's, . 


. 23 


Daniell's, 


27 


Q. 




Quicksilver, . 


. 101 


Quinia, 


. 276 


R. 




Radiant heat, 


. 46 


Transmission of 


50 


Repulsion, 


. 20 


Refraction, index of, 


53 


Resins, 


. 248 


Rhodium, 


100 


Rochelle salt, . 


254 


S. 





Safety lamp, . . . 245 
Invention of, . 243 
Saiicule, .... 250 
Salt radicals, the . 136, 178 
Salts, . . . 119, 183 



B 


CONTENTS. 






Page 


Page 


Salts of arsenic, . 


. 205 


Sulphuret, metallic, 


. 172 


boron, 


. 206 


Symbols, chemical, 


114 


chrome, . 


. 206 


T. 




silicon, 


. 206 


Tantalum, 


. 97 


Saxon blue, 


. 278 


Tartar emetic, 


255 


Selenium, 


91 


Tellurium, 


. 94 


Oxide of, 


. 144 


Theine, .... 


280 


Silica, 


. 160 


Thermo-electricity, 


. 73 


Silicon, 


. 87 


Thermo-multiplier, 


73 


Bromide of, . 


. 182 


Thermometer, 


. 24 


Chloride of, 


. 182 


Celsius's, . 


26 


Fluoride of, 


. 182 


Centigrade, 


. 26 


Salts of, . 


. 206 


Differential, 


25 


Silver, 


. 100 


Fahrenheit's, 


26 


Chloride of, 


. 197 


Reaumur's, 


26 


Nitrate of, 


. 202 


Thorina, 


. 166 


Sodium, 


. 107 


Thorium, 


1 % 06 


Chloride of, 


. 194 


Tin, .... 


. 98 


Fluoride of, 


. 199 


Oxides of, 


166 


Protoxide of, 


. 171 


Chlorides of, 


. 195 


Sulphuret of, 


. 173 


Titanium. 


96 


Soda, .... 


. 171 


Tungsten, . 


. 96 


Biborate of, 


. 206 


U. 




Dipyrophosphate of, 


. 204 


Ulmine, .... 


242 


Metaphosphate of, 


. 204 


Uranium, . 


. 97 


Pyrophosphate of, 


. 204 


Urea, . . . 


284 


Phosphate of, . 


. 204 


Urine, 


. 284 


Sulphate of, 


. 200 


V. 




Specific gravity, 


-. 14 


Vanadium, 


. 96 


Starch, 


218, 228 


Vaporization, . 


34 


Stearine, 


. 251 


Vapour, density of, 


. 34 


Steel, ... 


. 105 


Voltaic circles, 


66 


Stereoptene, 


. 247 


Volta electrometer, 


. 123 


Strontia, 


. 168 


W. 




Strontium, 


. 107 


Water, .... 


156 


Chloride of, . 


. 194 


Basic and constitu- 




Protoxide of, 


. 107 


tional, . 


. 189 


Sulphuret of, 


. 173 


Y. 




Strychnia, 


. 277 


Yttria, . . . . 


166 


Sugar, 


218, 228 


Yttrium, 


. 106 


of grapes, 


. 232 


Z. 




of milk, 


. 241 


Zinc, .... 


102 


Sulphocyanogen, 


. 269 


Oxide of, 


. 166 


Sulphur, 


. 88 


Chloride of, 


195 


Salts of, 


. 199 


Sulphuret of, 


. 174 


Sulphur salts, . 


. 208Zirconia, 


166 


Snlphurcts, 


. 172 


Zirconium, . 


. 106 



PREFACE 

TO THE FIRST EDITION. 



Dr. Whately, in his excellent Treatise on Rhetoric, has 
remarked that it is " impossible to lay down precise rules 
as to the degree of conciseness which is, on each occasion 
that may arise, allowable and desirable; but to an author 
who is, in his expression of any sentiment, wavering be- 
tween the demands of perspicuity and of energy, and doubt- 
ing whether the phrase which has the most forcible brevity, 
will be readily taken in, it may be recommended to use 
both expressions ; first to expand the sense, sufficiently to 
be clearly understood, and then to contract it into the most 
compendious and striking form." " The hearers," he adds, 
" will be struck by the forcibleness of the sense which they 
will have been prepared to comprehend ; they will under- 
stand the longer expression, and remember the shorter." 

The principle involved in these very just remarks has 
guided the compiler in preparing the following pages. At 
the stage in the progress of academical study in which 
chemistry is appropriately introduced, it is necessary to 
begin to accustom the student to instruction by means of 
lectures. The power of close and continued attention to 
spoken discourse, is an invaluable acquisition to the youth- 
ful mind, and one of the highest attainments of a well dis- 
ciplined intellect. There seems, indeed, to be no other 
method by which adequate instruction in the higher depart- 
ments of intellectual pursuits can be imparted, than by a judi- 
cious blending together of oral and written instruction, com- 
bining a full commentary in the form of lectures, with a text 
containing a clear and concise exposition of facts and prin- 
ciples. It is to this mode of instruction that the remarks 



10 PREFACE. 

we have quoted are applicable. The student will be struck 
by the forcibleness of the sentence which he will have been 
prepared to comprehend ; and he will thus understand, as 
well as remember, the shorter and concise expression of the 
principles that have been previously illustrated at length. 
To give full effect to this system of instruction, it will be 
necessary to require of the student that he take notes of the 
lecture, or prepare an abstract thereof, and undergo an ex- 
amination respecting such illustrations and experiments as 
are not contained in the text book. 

The study of chemistry appears to the compiler to be 
peculiarly adapted to familiarize a student to this mode of 
instruction. The science is one of details, so numerous 
and intricate, that the text book which should attempt to 
include them all, would be too cumbersome and overloaded 
with detail to admit of being thoroughly learned. A selec- 
tion of facts must therefore be made, and it seems most judi- 
cious to select such as are familiar and fundamental, or 
adapted to the illustration of principles, and to leave all be- 
yond this to the particular taste and views of the teacher. 
A text book, prepared according to this plan, appears to the 
compiler to be better adapted than any other for the pur- 
poses of academical instruction; for the great object of edu- 
cation, is not to convey a knowledge of the greatest possible 
number of individual facts, but to discipline the intellectual 
faculties, and prepare the youthful mind for the comprehen- 
sion of those general laws of nature, the knowledge of which 
chiefly distinguishes the civilized from the savage state— 
the cultivated and intellectual from the rude and uninformed 
individual. 

Those who may adopt the compiler's views, and use this 
little work as a text book, will find, in the excellent trea- 
tises of Drs. Silliman and Hare, a variety and multiplicity 
of experiments, which will render the preparation of lec- 
tures for illustrating the text, an easy task. 

Haverford, 11 mo., 14th, 1837. 



PREFACE 



SECOND EDITION. 

The changes which have taken place in the science, 
since the first edition of these Elements, have ren- 
dered it necessary to rewrite the greater part, so that 
it is almost a new work. The :5ader will see that 
the compiler is greatly indebted to Graham, Kane, 
Daniell, and Liebig, for the new matter which has 
been incorporated into the present edition. A trea- 
tise, so humble in its pretensions, will scarcely attract 
criticism; yet the author would observe, in defence 
of the arrangement he has adopted, that it has one 
advantage of practical utility to the teacher and the 
student, namely, that of spreading the experimental 
illustrations pretty equally over the whole course of 
instruction, an advantage which will, he thinks, be 
appreciated by competent judges. 

Haverford, 9mo. 2d, 1842. 



THE 



ELEMENTS OF CHEMISTRY. 



INTRODUCTION. 

1. Chemistry is that department of Physics which 
investigates the changes that take place in bodies, in 
consequence of their attraction or affinity for each 
other. 

2. The physical properties which depend on the 
powers of Gravitation, Cohesion, Heat, Light, and 
Electricity, form the subjects of the several depart- 
ments of natural philosophy. It is by these, and their 
other sensible properties, that we ascertain the iden- 
tity or diversity of bodies. Chemical changes more 
or less affect these properties, and some account of 
them seems therefore necessary as an introduction 
to the science of Chemistry. 



CHAPTER I. 

GRAVITATION AND COHESION. 

3. Attraction of Gravitation. — Light bodies 
which float on water, attract each other at percep- 
tible distances. The force of this attraction varies 
as the mass; and the velocity with which they ap- 

2 



14 ELEMENTS OF CHEMISTRY. 

proach each other depends on that force, so that if 
one of the bodies be twice the size of the other, the 
smaller body will move twice as fast as the larger. 
This velocity increases as their distance lessens, and 
the rate at which it increases is inversely as the square 
of the distance. 

4. All bodies whatever attract each other by this 
law. This force, which is called the attraction of 
gravitation, pervades the universe, and binds toge- 
ther the various systems of suns and planets. It is 
in virtue of this force, that all bodies tend to the earth 
in straight lines perpendicular to its surface. 

5. What we call the weight of bodies, is this ten- 
dency to the earth, measured by the force required 
to counteract it. It is important to have a fixed 
standard with which to compare the weight of other 
bodies. Water has been adopted for this purpose, 
as the standard for solids and liquids. This relative 
weight of bodies is called their specific gravity; in 
expressing it, the weight of water is taken as unity; 
so that when we state the specific gravity of a body 
to be 2 or 3, we mean that it is two or three times 
as heavy as an equal bulk of water. The specific 
gravity of a body is ascertained by weighing it in 
air, and afterwards in water. The loss of weight is 
the weight of an equal bulk of water; and this divi- 
ded into the weight in air, gives the relative weight 
or the specific gravity of the body. 

The weight of a cubic foot of water is nearly 997 
avoirdupois ounces; so that if the specific gravity 
of water be taken at 1000, the specific gravity of a 
body will express very nearly the weight in ounces 
of a cubic foot of its mass. The weight of the at- 
mosphere at the temperature of 60° F., and under a 
barometric pressure of 30 inches, is the standard, with 
which the weight of all other gases at the same tem- 
perature and under the same pressure is compared. 
In order to compare the two standards, we must 



ATTRACTION OF COHESION. 15 

divide the specific gravity of gases by 815, which 
will give their weight as compared with that of 
water. 

6. Attraction of Cohesion. — It is in virtue of 
this attraction, that the particles of bodies cohere 
in masses. Fluidity and solidity, with its various 
degrees of elasticity, tenacity, ductility, toughness, 
softness, friability and hardness, are various modified 
effects of this cohesive force. The tendency of this 
attraction being to draw the particles of bodies to 
each other, it would, if left to itself, bring them into 
actual contact. But it is certain that no two parti- 
cles of matter really touch each other, for there is no 
body which does not contract in all its dimensions 
by cold. It seems manifest, therefore, that every 
material particle must exert a repulsive as well as 
an attractive force. If the former decrease more 
rapidly than the latter as the distance increases, it 
may be powerful enough to prevent the particles 
from coming into contact, and yet give place at a 
certain distance to the latter. The equilibrium of 
these opposite forces will explain fluidity, and the 
toughness and adhesiveness of many substances; for 
if it were the only cause of cohesion, a sliding mo- 
tion among the particles would always be possible 
when the two forces were in equilibrium. 

7. In order to explain the immoveability of the 
particles in m ost solids, we must resort to an addi- 
tional supposition. If we conceive every particle of 
matter to be like a small magnet possessing opposite 
points or poles, each of which repels the same point 
or pole in every other particle, while it attracts the 
opposite, it is clear that the arrangement of the par- 
ticles will be determined by the axes of polarity; and 
that firm solids of a definite figure, will be the result 
of arranging the opposite poles so as to connect with 
each other. 

8. Crystallization. — Bodies often cohere in masses 



16 ELEMENTS OP CHEMISTRY. 

of no determinate shape, which are called amorphous. 
But by allowing them to pass slowly from a fluid to 
a solid state, most bodies assume regular or crystal- 
line forms. These crystals are generally bounded 
by polished plane surfaces. The same body in crys- 
tallizing, often assumes a great variety of forms, all 
of which are found to be modifications of one origi- 
nal or primitive crystal. The laws which regulate 
this deviation from the form common to them all, 
admit of mathematical investigation, and are the 
subject of the science of Crystallography. A know- 
ledge of them is so far important to the chemist, as 
to require a brief explanation in this place. 

9. All those crystals which may be derived from 
one another, and which can be deduced from the 
same primitive crystalline form, are said to belong 
to the same crystallographic system. What is meant, 
may be illustrated by the changes of which the cube 
is susceptible. If we suppose the solid angles of the 
cube to be cut off or truncated by planes at right an- 
gles to its solid diagonal, we shall change its figure 
into an octohedron, the six solid angles of which are 
in the centres of the six plane faces of the cube. It 
is obvious that this process of truncation may stop 
at any stage of its progress, so that the resulting 
figure shall preserve the form either of a cube or an 
octohedron with its solid angles truncated. It is also 
obvious that the process may be reversed, and the 
cube formed from the octohedron by the truncation 
of its solid angles. 

10. If lines be conceived to be drawn from the 
opposite solid angles of the octohedron, there will be 
three equal lines or axes passing through the centre 
of the crystal. These lines will coincide with those 
drawn through the centre of the opposite faces of the 
cube. The cube and the octohedron are therefore 
said to possess the same crystallographic axes; that 
is to say, the axes passing through the centre of the 



CRYSTALLIZATION. 



17 



crystal from opposite solid angles, or the centres of 
opposite faces, coincide. 

1 1 . If the edges of the cube be truncated by planes 
parallel to the respective diagonal planes of the cube, 
the resulting figure will be the regular rhomboidal 
dodecahedron, the six acute angles of which are in 
the centre of the six faces of the cube. This figure 
is, therefore, said to possess the same crystallogra- 
phic axes as the cube and octohedron. If the edges 
of the cube be bevelled, that is to say, cut off by two 
planes equally inclined, instead of one, the resulting 
figure will be a cube with four low pyramids on 
each face, and which, from its general resemblance 
to that solid, is called the tetra hexahedron. By va- 
riously bevelling the edges and angles of these crys- 
tals, we obtain as many various crystalline forms, 
all of which are said to belong to the same system; 
that is to say, they possess the same crystallographic 
axes. 

12. A clearer notion of the nature of crystals may 
be gained by conceiving what must be the structure 
of the cube. The cube may be conceived to be 
formed in the following manner. Eight particles 
can be arranged so as to form a minute cube, each 
face of which contains two rows of particles. This 
can be increased to any size by the successive ad- 
dition of layers of particles each consisting of a row 
more than the layer on which it is imposed. If, 
when it has gained a certain size, when, for exam- 
ple, it consists of seventeen rows of particles on 
each face, the law of increase be changed and each 
successive layer consist of two rows less than the 
one beneath, a square pyramid eight rows in height 
will be built up, on each face of the cube, and the 
adjacent sides will be in the same plane, so as to 
form the regular rhomboidal dodecahedron. If the 
law of decrement, as it is termed, be more rapid 
than two rows for every additional layer, the adja- 

2* 



18 



ELEMENTS OP CHEMISTRY. 



cent sides of the pyramid will not be in the same 
plane, and the 24-sided figure already spoken of as 
the tetra hexahedron will be formed. We can easily 
frame the law of decrement by which the regular 
octohedron can be conceived to be formed from the 
cube, and vice versa. 

13. It has already been said that in order to ex- 
plain the hardness of firm solids, the existence of 
opposite poles of attraction and repulsion in the par- 
ticles of matter must be assumed. Polarities of this 
kind must also be taken for granted in any theory 
of crystallization, and if they exist, it is evident that 
there will be lines or planes of stronger and weaker 
attraction, and that the crystal will more easily split 
in the latter than in the former direction. Such is 
found to be the case. 

All the various crystalline forms which the same 
substance is capable of assuming, are, as has been 
said, modifications of one primitive form, and all 
such crystals are found to split with plane polished 
surfaces in planes parallel to the planes of this primi- 
tive form, and they admit of cleavage in no other 
direction. We can hence ascertain by means of their 
cleavage, the primitive form of those crystals, of 
which only the secondary or derived forms are found 
in nature. 

The cube or hexahedron, the regular octohedron, 
and rhomboidal dodecahedron, have the same crys- 
tallographic axes and belong to the same crystallo- 
graphic system. 

14. There are seven primary forms of crystals, in- 
capable of being reduced to each other according to 
the known laws of crystallography, giving rise to all 
the various secondary forms that occur in nature, 
and characterized by the number, length, and posi- 
tion, of their crystallographic axes. 

The first of these is the cube which has three 
equal rectangular axes. It constitutes the class Mono- 
metrica. 



CRYSTALLIZATION. 1 9 

The second is the square prism, which has all the 
axes rectangular; the two horizontal ones equal, and 
the vertical either greater or less than the others. It 
forms the class Dimetrica. 

The third is the right rectangular prism which has 
all the axes unequal and rectangular. It forms the 
class Trimetrica. 

The fourth is the right rhombic prism, the lateral 
axes of which, intersect each other obliquely, while 
they are both at right angles to the vertical axis. It 
is the class Monoclinata. 

The fifth is the oblique rectangular prism, 
which has its lateral axes at right angles to each 
other while both of them are oblique to the vertical 
axis. It is the class Diclinata. 

The sixth is the oblique rhomboidal prism, which 
has all its three crystallographic axes oblique to each 
other. It is the class Triclinata. 

The seventh is the regular rhombohedron, which 
is a solid whose faces are six equal rhombs. Each 
face has therefore two acute and two obtuse angles 
opposite to each other. The solid angles of the 
rhombohedron are thus formed either by three acute 
or three obtuse plane angles, or by two obtuse and 
one acute, or by one obtuse and two acute plane 
angles. The crystal is said to be in its proper posi- 
tion when the axis passing through the solid angles 
bounded by similar plane angles is perpendicular to 
the horizon. The other six angles will then be 
symmetrically ranged round the vertical axis, and 
the lines uniting them through the centre of the solid 
are called the lateral axes. This figure has there- 
fore four equal crystallographic axes. It is the class 
Tetraxona. 

The first of these systems is the only one of which 
the forms are all interchangeable and the axes inva- 
riable. The proportions and inclinations of the crys- 
talline axes in the other systems vary indefinitely, 
and as they do not change in the same mineral, the 



20 ELEMENTS OF CHEMISTRY. 

measurement of the angles of crystals, in order to 
ascertain the dimensions of their primary form, be- 
comes one of the most valuable means of determining 
the species of crystalline minerals. 

15. The laws by which the edges and solid angles 
are truncated, are such that the resulting figure pos- 
sesses either the same axes as the primary, or axes 
which are in a definite multiple ratio to them. By 
the truncation of the various prisms are formed the 
several varieties of the octohedron. The hexagonal 
prism is the result of the truncation of the lateral 
angles of the rhombohedron by vertical planes. 

These explanations seem necessary in order to 
prepare the student to understand the value of a 
similarity in crystalline forms as an indication of 
similarity in the composition of bodies. 

16. Repulsion. —The repulsive force, which is the 
antagonist power of cohesion, is evidently the prin- 
ciple, or matter, or force, which is the cause of the 
sensation of heat. To this unknown cause the name 
Caloric has been given. The examination of its 
nature and properties constitutes a distinct depart- 
ment of science, and it is with its relations to the 
force of cohesion that we are mainly concerned in 
chemistry. 

Those general properties of bodies which depend 
less on the nature of their component parts than on 
their state of aggregation, will be found to be prin- 
cipally the results of these two forces of cohesion 
and caloric. 



CHAPTER II. 

CALORIC. 



17. It is by means of our sensations of warmth 
and cold that we acquire our first knowledge of the 
existence of such an agent as caloric. Our fur- 



,! 



EXPANSION. 21 

ther acquaintance with its properties is derived 
from observing the changes which bodies undergo 
in circumstances which affect us with either of 
these sensations. Whatever caloric be, it is evident 
that it tends to diffuse itself among all the bodies 
within its influence, for cold bodies brought near to 
warm ones always become warm. This is evident 
to a sentient being from his feelings, and it is proved 
by the changes which bodies thereby undergo. We 
must therefore examine in the first place, what those 
changes are, and in the second, how they are pro- 
duced. The most striking are those which take 
place in their state of aggregation, and in their di- 
mensions. Water is changed by cold into a firm 
solid, and it boils and is converted into vapour when 
heated. Observation proves that these changes take 
place at constant degrees of heat, and they therefore 
furnish us with fixed points beyond, and between 
which, we can determine other effects of caloric. 

IS. Expansion — If a bar of iron be cooled to the 
temperature of melting ice, and a piece of it, pre- 
cisely three feet long, be then cut off, and if the 
piece be immersed in boiling water, it will be found, 
by accurate measurement, that it has gained the 23d 
part of an inch in length. By the same change of 
temperature, a glass rod of equal dimensions would 
be lengthened the 35th, a rod of brass the 15th, and 
one of lead the 10th part of an inch. 

By exposing these bars to a still greater degree of 
heat, they will be found to expand still more, and in 
the same relative order. If, after having thus heat- 
ed them, we again immerse them in melting ice, we 
shall find that they have recovered their original 
length. 

If, instead of a bar, we try the experiment on a 
cube of either of these substances, we shall find that 
it has expanded equally in all its dimensions. 

These experiments prove that solid bodies expand 



22 ELEMENTS OF CHEMISTRY. 

by heat, and contract by cold; and that different 
bodies do not expand equally by the same increase 
of temperature. 

19. The following table exhibits the expansion of 
several substances when heated from the freezing to 
the boiling point of water. 

English flint glass, - - - T _i_ of its length. 

Glass tube without lead, - ^ TT " 

Platinum, nk? " 

Untempered steel, - - - ¥ | T " 

Tempered steel, - - - - ¥ -i y " 

Gold i " 

\JOlU, ------- .___. 

Copper, T * T " 

Brass, T | ¥ " 

Silver, r ^ « 

English tin, ^ « 

Lead, ¥ | T " 

Three times the expansion in length will be a very 
close approximation to the total increase in bulk of 
the substance. 

20. The pyrometer is an instrument for rendering 
sensible the expansion of solid bodies by different 
degrees of heat. A rod of metal, or any other sub- 
stance, the expansion of which is to be tried, is laid 
upon two supports on the base of the instrument. 
One end touches the short arm of an upright lever, 
the long arm of which is connected with the short 
arm of an index. The other end of the rod is ad- 
justed, and kept from moving, by means of a screw. 
The levers are so adjusted that the expansion of the 
bar is multiplied 100 times by the index, and if the 
rod be ten inches in length, and the degrees of the 
scale are an inch long, a motion of the tenth of a 
degree by the index will measure an expansion of 
the rod equal to 1000th part of its length. The heat 
is applied to the rod by means of a small spirit lamp. 
When it is wished to ascertain the expansion be- 
tween the temperature of freezing and boiling wa- 



EXPANSION. 23 

ter, the rod is passed through water-tight collars in 
the ends of a long metallic box containing water, to 
which heat is applied. 

BregueVs pyrometer is a very delicate instrument 
for measuring small changes of temperature, and 
consists of a narrow metallic slip, about ^^ of an 
inch thick, composed of silver and platinum soldered 
together, and coiled in a cylindrical form. The top 
of this spiral tube is suspended by a cross-arm, and 
the bottom carries, in a horizontal position, a very 
delicate golden needle, which traverses as an index 
on a graduated circular plate; a steel stud rises in 
the centre of the tube to prevent its oscillating from 
a central position. If the silver be on the outside of 
the spiral, the influence of increased temperature 
will increase the curvature, and move the appended 
needle in the direction of the coil, while the action 
of cold will relax the coil, and move the needle in 
an opposite direction. 

21. The cohesive attraction lessens as the distance 
between the particles increases; it therefore follows 
that bodies expand more by equal increments of heat 
at high, than at low temperatures. This is ascer- 
tained by experiment to be the case. Hallstrom 
found that a bar of iron of which the length was 1. 
at the freezing point of water, lengthened to 1.001446 
when heated to its boiling point. Dividing the dif- 
ference of temperature into five equal intervals, he 
found the expansion for the 

First interval to be - - .000211 

Second " - - .000242 

Third " - - .0002S1 

Fourth " - - .000329 

Fifth " - - .000383 

It also follows that liquids expand more by heat 

than their respective solids, and it is found that 

liquids expand generally more than solids. 

If several glass tubes of equal diameter, open at 



24 ELEMENTS OF CHEMISTRY. 






one end, and terminating at the other in bulbs of 
equal size, be partially filled, one with alcohol, one 
with olive oil, another with water, and another with 
mercury, at the common temperature, and be then 
placed in hot water, it will be seen that the fluids all 
rise in the tubes, and that the alcohol expands most 
and the mercury least. It is therefore, evident that 
they expand more than glass, for if the glass ex- 
panded as much as the contained liquid, there would 
be no relative change of bulk. 

If the interval between freezing and boiling water 
be equally divided, and the expansion of these liquids 
in the warmer interval be taken at 15, their expan- 
sion during the colder half will be as follows: mer- 
cury 14, olive oil 13.4, alcohol 10.9, and water 4.7. 
This experiment proves that liquids as well as solids 
expand more by equal increments of heat at high, 
than at low temperatures. 

22. It follows from what has been said, that as 
there is no cohesive force to overcome in gases, they 
must all be expanded alike by equal increments of 
the repulsive force." This is verified by experiment. 
It appears from the researches of Gay Lussac, that 
100 cubic inches of atmospheric air, in being heated 
from the freezing to the boiling point of water, ex- 
pand to 137.5 cubic inches. All the gases which 
have been subjected to the same trials, expand by 
the same quantity; and it is ascertained that the 
rate of expansion is uniform between the freezing, 
and the boiling point of mercury. 

This uniform or nearly uniform expansion of 
most bodies by equal increments of heat, enables 
us to construct the thermometer, an instrument, by 
which we measure those changes of heat and cold 
designated by the word temperature, with an accu- 
racy which our own feelings are incapable of attain- 
ing. 

As atmospheric air expands equally for equal in- 



EXPANSION. 25 

crements of heat, it forms a perfectly accurate mea- 
sure of the change of temperature. The construction 
of the air thermometer is extremely simple: a glass 
tube, of an uniform bore, is to be selected for the 
purpose, and one end of it is blown into a spherical 
ball, while its other extremity is left open. After 
expelling a small quantity of air by heating the ball 
gently, the open end of the tube is plunged into 
coloured water, and a portion of the liquid is forced 
up into the tube by the pressure of the atmosphere 
as the air within the ball contracts. In this case, it 
indicates changes of temperature with extreme deli- 
cacy, and the alternate contraction and expansion of 
the confined air, may be measured by the alternate 
ascent and descent of the coloured water in the stern. 
This instrument is, however, affected by the varying 
pressure of the atmosphere upon the liquid in the 
vessel, as well as by heat; and the expansion and 
contraction of the confined air are so great that it can 
only be used for small variations of temperature. 
The air thermometer is, therefore, seldom employed, 
except in a modified form, called the differential 
thermometer. This instrument consists of two thin 
glass bulbs at the extremity of a tube, bent twice at 
right angles. Both bulbs contain air; but the greater 
part of the tube is filled with coloured sulphuric acid, 
so that, when the air in both bulbs is at the same 
temperature, the fluid in both stems is at the same 
height. The slightest difference between the tem- 
perature of the two balls will cause the liquid to rise 
in the tube next to the ball, the temperature of which, 
is relatively lower. A graduated scale is affixed to 
one of the tubes, by means of which the changes of 
this instrument can be compared with those of a 
common thermometer. 

23. The expansion of mercury between its freez- 
ing and boiling point furnishes us with the most ac- 
curate and convenient measure of these changes. 



26 ELEMENTS OF CHEMISTRY. 

The mercurial thermometer is constructed by nearly 
filling with mercury, a glass tube of uniform bore, 
having a bulb at one end. The mercury is then 
heated till it fills the tube, or boiled till the atmos- 
pheric air within the tube is replaced by mercurial 
vapour, and the tube is then hermetically sealed. 
The tube is attached to an ivory or metallic plate 
upon which the scale of temperature is marked. In 
order to graduate the instrument, it is dipped into 
melting ice or snow, and the point to which the mer- 
cury sinks is marked on the scale. Another mark 
is made opposite to the place in the tube to which 
the mercury rises when the instrument is dipped in 
boiling water. The space between these two points 
has been variously divided into degrees by different 
philosophers. 

Reaumur, whose thermometer is used in France, 
called the freezing point 0°, and the boiling point S0°. 
Celsius, a Swedish naturalist, called the former 0°, 
and the latter 100°. Four degrees of the former, 
are therefore, equivalent to five of the latter, which 
is often called the centigrade thermometer. 

In Great Britain and America, the graduation 
contrived by a Dutch instrument maker, named Fah- 
renheit, is in general use. Fahrenheit conceived that 
the cold produced by a mixture of equal parts of 
snow and salt, was the greatest that could be obtain- 
ed. He, therefore, in graduating his instrument, 
made a third mark at the point to which the mercury 
sunk in such a mixture, and called this 0°, or zero. 
He divided the space between the freezing and the 
boiling points of water into 180°, and, by continuing 
the graduation downwards, he found that there were 
thirty-two of these degrees between the freezing 
point and his zero. He, therefore, called the former 
32°, and the boiling point 212°. In order to reduce 
the degrees of Reaumur to those of Fahrenheit, mul- 
tiply them by 2i, and to the product add 32, when 



EXPANSION. 



27 



the degrees are above, and subtract it, when they are 
below 0°. To find the degrees of Fahrenheit equi- 
valent to those of Celsius, multiply by f , and add or 
subtract 32 as before. 

Although mercury expands more at high, than at 
low temperatures, yet as the glass which contains it 
has the same law of increased expansion, the one 
compensates for the other, and the scale may be ex- 
tended without material error, both upwards and 
downwards from the boiling and freezing points of 
water. Mercury boils at 662° F. (350° C.) on the 
scale so extended, and becomes solid at — 39° F. 
( — 39i° C), which is the greatest range of any ther- 
mometry scale. Thermometers may be constructed 
of alcohol, which remains fluid at the lowest tem- 
perature to which it has hitherto been exposed; but 
this liquid boils at a heat below the boiling point of 
water, so that mercury is by far the most useful liquid 
for thermometers. The absolute expansion of mer- 
cury, in passing from the freezing to the boiling point 
of water, is T yy^.; which gives the expansion for 
each degree of Fahrenheit TT \ ■$ , and for each degree 
of the centigrade yyVo-. 

24. For measuring high degrees of heat, various 
modifications of the Pyrometer have been invented. 
The most accurate of these is Daniell's pyrometer, in 
which the temperature is measured by the expan- 
sion of a platinum rod. It consists of two parts, a 
register and a scale. The former is a bar of black 
lead earthenware, in which is drilled a hole, into 
which a cylindrical rod of platinum, of nearly the 
same diameter, is introduced so as to rest against the 
solid end of the hole. Upon the outer end of the 
rod, rests a cylindrical piece of porcelain, which is 
firmly secured in its place. The scale consists of 
two rules of brass fitted to the end of the register, by 
means of which, the actual expansion of the rod is 
multiplied and measured on the arc of a circle, in the 



28 ELEMENTS OF CHEMISTRY. 

same manner as in the common pyrometer. The 
total expansion of the black lead case is so small that 
it may be neglected without any sensible error, and 
the whole register is infusible in any heat that has 
hitherto been obtained in a furnace. When the 
register is exposed to a great heat, the expansion of 
the metallic rod pushes forward the cylinder of por- 
celain, which remains in the position which is thus 
given to it. After the instrument has cooled, it is 
applied to the scale, which measures, with minute 
accuracy, the expansion the rod has undergone in 
consequence of the heat into which it has been ex- 
posed. 

25. There is a remarkable exception to this law 
of expansion by heat. Certain fluids as they ap- 
proach the freezing point, cease to contract, and then 
begin, and continue to expand as the temperature is 
lowered. Water is an instance of this anomaly ; for 
its point of greatest density is at the temperature of 
38.97° (3.87° C), and it then begins to expand at the 
same rate by which it contracted, so that its bulk at 
32° (0°) is equal to that which it possesses at 45.94° 
(7.74° C.). This expansive force of water, as it ap- 
proaches congelation, is an agentof prodigious power. 
In one experiment it was sufficient to burst a strong 
brass globe, the cavity of which was an inch in 
diameter ; and it was estimated to be equal, in this 
case, to an actual pressure of 27,720 pounds. The 
most probable supposition which has been made of 
the cause of this phenomenon, is, that, as they ap- 
proach the freezing temperature, the particles of 
water begin to assume a certain crystalline arrange- 
ment, in virtue of which they occupy a greater space 
and expand. A beneficial consequence of this law 
is, that ice is always lighter than water, and that the 
water at the bottom of fresh water lakes and rivers 
is never frozen. 

Other liquids, besides water, obey this remarkable 



CAPACITY FOR HEAT. 29 

law. Melted iron and bismuth expand in becoming 
solid, while mercury undergoes a sudden contrac- 
tion. 

26. Capacity for Heat. — If equal quantities of any- 
fluid, unequally heated, be mixed together, the tem- 
perature of the mixture will be the exact mean of 
the temperatures of the separate quantities before 
they were mingled. For example, a pound of water 
at 160°, being mixed with a pound of water at 40°, 
the temperature of the mixture will be 100°, proving 
that the quantity of caloric which a pound of water 
parts with in being lowered 60°, is precisely that 
required to raise an equal quantity of water the same 
number of degrees. 

27. If, however, we mix a pound of water at 160° 
with a pound of spermaceti oil at 40°, the tempera- 
ture of the mixture will not be, as before, 100°, 
which is the mean, but 120°, and if the oil is 160° 
and the water 40°, the temperature of the mixture 
will be 80°. If again a pound of water at 160° be 
mixed with a pound of mercury at 40°, the tempe- 
rature of the mixture will be 155°, and if the water 
be 40°, and the mercury 160°, the temperature of 
the mixture will be 45°. From these experiments 
we learn that bodies are unequally heated by the 
same quantities of heat. The caloric which will 
raise the temperature of a pound of water from 40° 
to 50°, will raise a pound of oil from 40° to 60°, and 
a pound of mercury from 40° to 270°. 

28. The same fact may be proved by means of 
the quantity of ice at 32°, which different substances 
will melt in being lowered a certain number of de- 
grees. The instrument for performing these experi- 
ments is called a calorimeter. The substance to be 
experimented on, is placed within a vessel containing 
ice, which is kept at 32°, by being surrounded by 
melting ice in an outer vessel. The melting of the 
ice in the inner vessel is owing solely to the heat 

3* 



30 



ELEMENTS OP CHEMISTRY. 



communicated from the heated body within, and the 
water it forms is carefully drained off and weighed. 
In this manner it has been ascertained that a pound 
of water, in cooling a certain number of degrees, will 
melt 23 times as much ice, and a pound of sperma- 
ceti oil, Hi times as much as a pound of mercury, 
under the same circumstances. It is also ascertained, 
that other different substances melt different quan- 
tities of ice, under similar circumstances. 

29. It is therefore conceived that the absolute 
quantity of caloric, which is contained in bodies, must 
vary, and that each substance, in passing from lower 
to higher temperatures, combines with or absorbs 
greater or less quantities of caloric, according to its 
own law of affinity or absorption. Hence, if we 
take the relative quantities of heat requisite to raise 
different bodies the same number of degrees of the 
thermometer, as the nearest measure we can obtain 
of the actual quantities thus absorbed, water may be 
regarded as having 23 times as great a power of 
absorption, or as it is termed capacity for heat, as 
mercury, and twice as great a capacity as oil. 

We have no means of ascertaining in any case 
the absolute quantity of caloric in combination with 
bodies, and the closest approximation we can make 
to it, is this determination of the specific heat, as it 
is termed, that is, the relative quantities, absorbed or 
given out by bodies in undergoing equal changes of 
temperature. 

30. If this power of absorbing caloric, whether it 
be termed affinity or capacity for heat, or specific 
heat, be diminished in any body, it is evident that a 
portion of the combined caloric will be disengaged, 
or set free, and that the temperature will rise. If, 
on the contrary, it be increased, the body will absorb 
caloric and the temperature will fall. Gases are of 
all bodies those whose capacity for heat is most easily 
affected. Condensation decreases and rarefaction 



HEAT OF FLUIDITY. 31 

increases their specific heat, and hence the former 
raises and the latter lowers their temperature. For 
example: if air be suddenly compressed in a con- 
densing syringe, the heat disengaged in consequence 
of the sudden reduction of its specific heat, will be 
sufficient to set fire to tinder, and a flash of light will 
at the same moment be visible. Again, a thermo- 
meter placed in the receiver of an air pump, uni- 
formly falls during the process, and in proportion to 
the progress of exhaustion, and rises again upon the 
admission of the air. This fact has been applied to 
the explanation of the intense cold, experienced in 
the upper and rarefied portions of the atmosphere. 

31. The specific heat of a body varies with its 
state of aggregation. The only substance of which 
the specific heat is known in these various states is 
water; that of ice being .9; of water 1.; and of steam 
.847. 

32. The following table exhibits the specific heat 
of several substances, chiefly determined by Reg- 
nault, (Kane, p. 101.) 

Water, 1,000 Silver, .057 

Carbon, .241 Tin, . .056 

Sulphur, .202 Mercury, .033 

Iron, .114 Platinum, .032 

Zinc, .095 * Gold, .032 

Copper, .095 Lead, .031 

33. Heat of Fluidity. — An increase of its sensible 
temperature is the surest indication we possess of the 

\ passage of caloric into a body. By reason of the 

tendency of caloric to an equilibrium, the sensible 

. temperature of cold bodies, that are placed within 

the influence of warmer ones, is steadily and equally 

! increased. 

j 34. There are two remarkable exceptions to this 

i law. If ice, wax, and lead, each of the same tem- 

! pcrature, say 0°F. ( — 17.77° C.) be exposed alike to 

a heat equal to that of boiling mercury, they will ali, 



32 ELEMENTS OF CHEMISTRY. 






for a time, exhibit a steady increase of temperature. 
If the bulb of a thermometer be inserted in a hole in 
the middle of each, so as to mark its temperature, 
the following changes will take place. When the 
thermometer inserted in the ice rises to 32° F. (0° 
C.) it will become stationary, although those placed 
in the wax and lead continue steadily to rise. 

The thermometer inserted in the ice remains sta- 
tionary at 32°, until all the ice is melted, and then 
again rises as before. In like manner the thermo- 
meter placed in the wax, continues to rise, till it 
reaches the temperature of 136° F. (57.77° C.) when 
the wax begins to melt. It remains stationary until 
the wax is all melted, and then again rises as before. 
The same temporary suspension of the rise of the 
thermometer, inserted in the lead, occurs, when it 
reaches the temperature of 612° F. (322.2° C.) the 
fusing point of that metal. 

35. Although from its known properties, we may 
be sure that caloric has, during all this time, been 
passing into the ice, the wax, and the lead, there has 
been an interval, that, namely, of their passing into 
the fluid state, during which they gave no indication 
by the thermometer of an increase of temperature. 
The heat, therefore, which it received during this 
period, was employed in melting the body, and not 
in raising the sensible temperature. The unavoid- 
able inference is, that during the process of fusion a 
portion of caloric has combined with the body, in 
such a way, that its presence is not indicated by the 
thermometer. 

36. The caloric which is thus absorbed by solids 
in becoming fluid, is given out by fluids in becoming 
solid. Although the freezing point of water is 32° 
F. (0° C.) it may, by being kept perfectly still, be 
cooled to 22° F. (—5.55° C.) If it be then suddenly 
agitated, the temperature of the whole mass will be 
raised to 32° F., and a portion, which Dr. Thompson 



HEAT OF FLUIDITY. 33 

ascertained to be -^ of the whole quantity, will at 
the same time be congealed. The caloric given out 
in the act of congelation by that portion of the water 
which has become frozen, has therefore been suffi- 
cient to raise fourteen times its quantity of water, ten 
degrees of the thermometer; or, in other words, it is 
sufficient to raise its own bulk of water, 140 degrees 
of the thermometer. 

37. That this is the quantity of caloric the ice had 
absorbed in becoming fluid, is proved by the follow- 
ing experiments. If equal weights of water and ice, 
both indicating 32°, be exposed alike to the tempe- 
rature of boiling water, it will be found as before, 
that a thermometer placed in the ice will not begin 
to rise till it is all melted, at which time that im- 
mersed in the water will indicate 172°, proving that 
140° of heat had become latent^ as it is termed, in 
the fusion of the ice. If, again, a pound of ice at 
32°, be immersed in a pound of water at 172°, the ice 
will be melted, and the temperature of the whole 
will be 32°, which satisfactorily shows that in be- 
coming fluid, the ice had absorbed and rendered 
insensible to the thermometer, the caloric which an 
equal quantity of water had given out in falling 140°. 

38. Irvine determined the quantity of heat ren- 
dered latent in certain bodies during the process of 
liquefaction, by noting the rise of the thermometer 
when it was immersed during the same period, and 
under the same circumstances, in an equal quantity 
of the same body in a fluid state. The results are 
given in the second column of the following table, 
while the numbers in the third are the latent heat, 
as compared with that of water. 

Water, 140° 1000. 

Sulphur, 143.68 207.3 

Zinc, 493. 334.5 

Tin, 500. 200. 

Bismuth, 550. 113. 



34 ELEMENTS OF CHEMISTRY. 

39. This absorption of caloric in the process of 
liquefaction, has been applied to the production of 
extreme degrees of cold. Solutions in water, and in 
certain acids, of various salts, are liquid at very low 
temperatures; and when they are formed by mixing 
their elements in a solid and finely divided state, the 
liquefaction takes place suddenly with so rapid an 
absorption of caloric from the surrounding bodies, as 
greatly to reduce the temperature. Thus a mixture 
of two parts by weight of snow, with one of com- 
mon salt, reduces the thermometer to — 5° F., and a 
mixture of two parts of snow with three of chloride 
of calcium, lowers the temperature from 32° F. to 
— 50° F. To ensure success in these experiments, 
the salts must be newly crystallized and finely pow- 
dered, and the materials must be previously cooled 
in a freezing mixture. 

40. Vaporization. — All bodies, as has been alrea- 
dy observed, exist either in the solid, liquid, or aeri- 
form state, according to the proportions of caloric 
with which they are combined. The same pheno- 
menon that takes place in liquefying solids, namely, 
that of rendering latent a large and definite portion 
of caloric, is essential to the conversion of liquids 
into gases. This conversion takes place even at very 
low temperatures. The upper or superficial stratum, 
not only of liquids, but of certain solids, appears to 
possess the power of absorbing, and rendering latent, 
the caloric which exists in a free state in the sur- 
rounding medium, and thus of imperceptibly and 
continually assuming the gaseous form. The num- 
ber of superficial particles which admit of being thus 
rendered gaseous, depends jointly upon the sensible 
temperature and the affinity of the body for caloric. 

41. The density of the vapour of any given body 
which is capable of existing at a given temperature, 
is a constant quantity. This may be readily proved 
by taking two glass tubes closed at one end, filling 



VArORIZATION. 35 

them with recently boiled mercury, and inverting 
them over mercury. They will both indicate the 
same pressure of the atmosphere by the equal height 
of the mercurial column. If a small quantity of 
water be introduced into the upper part of one of the 
tubes, and its temperature be gradually raised from 
32° F. (0° C.) to 212° F. (100° C), it will be found 
that the pressure of the vapour which exists at the 
respective temperatures will be as stated below, 
being measured by the depression of the column of 
mercury in the tube that contains the water, below 
the height that it stands in the other tube. 

32° 0.2 inches 100° 1.86 inches 
50 0.375 " 150 7.42 " 
60 0.524 " 212 30. * 

42. These pressures are found to be constant at 
the same temperatures, and to be altogether inde- 
pendent of the presence of any other gas; or, in other 
words, the quantity of the vapour of water capable 
of existing at a given temperature, is dependent 
solely upon the temperature. This is ascertained to 
hold respecting all other liquids upon which experi- 
ments have been tried, and is therefore regarded as 
an universal law. 

43. As only a certain density of vapour can exist 
at a given temperature, evaporation goes on from 
the surface of a liquid until that density be attained. 
The rapidity with which it proceeds will therefore 
increase in proportion to the warmth and dryness 
of the air, and to the extent of surface. It is also 
increased by a current which continually brings 
new portions of air into contact with the surface of 
the liquid. Although the quantity of vapour capa- 
ble of existing at a given temperature is altogether 
independent of the density of the atmosphere, this 
density greatly affects the rapidity of evaporation. 
In a vacuum water boils at 70°, and if means be 
taken to absorb the vapour as fast as it is formed, 



36 ELEMENTS OF CHEMISTRY. 

the caloric abstracted from the water and rendered 
latent by the portion which is converted into vapour, 
will cause the remaining liquid to freeze. This may 
be shown by placing two shallow vessels, one con- 
taining sulphuric acid and the other water, under an 
exhausted receiver. The acid absorbs and removes 
the vapour as fast as it is formed, until at length the 
water is frozen. 

44. Advantage has been taken of this law to sepa- 
rate two mixed liquids, by exposing them in vacuo 
to a substance which absorbs the vapour of one and 
not of the other. If a mixture of alcohol and water 
be placed in the upper vessel described above, and 
the receiver be exhausted, it will soon be filled with 
the vapour of both liquids at their maximum densi- 
ty. But if the lower vessel be filled with dry quick 
lime, the aqueous vapour will be absorbed as fast as 
it is formed, and thus a continual evaporation of the 
water will take place, until at length the alcohol, 
which does not evaporate, is left pure. 

45. The Cryophorus of Dr. Wollaston, is an in- 
strument for illustrating' these laws. It is a glass 
tube, bent in a right angle at each extremity, and 
then terminating in a bulb. One of the bulbs is half 
filled with pure water, the air is entirely expelled, 
and the tube hermetically sealed. On placing the 
empty bulb in a freezing mixture, the vapour is con- 
densed in it as fast as it is formed in the other bulb, 
the evaporation in which goes on so rapidly as to 
congeal the remaining water. 

The pulse glass is a small instrument on a similar 
principle, for exhibiting the low temperature at 
which water boils in a vacuum. 

46. It will be seen, by reference to the table on 
page 35, that at the boiling point of water the pres- 
sure of its vapour upon the surface of the liquid is 
equal to that of the atmosphere. The phenomenon 
of ebullition arises from this circumstance, and the 



CRYOPHOROUS. 37 

agitation of the liquid, which we call boiling, is 
caused by the rapid formation of bubbles of aqueous 
vapour throughout the body of the liquid; for until 
the elasticity of the vapour is equal to that of the at- 
mosphere, it is only the superficial stratum of parti- 
cles that is converted into gas, and the process of 
heating the fluid goes on without disturbance. As 
ebullition takes place whenever the elasticity of the 
vapour that is formed is sufficient to overcome the 
pressure of the atmosphere upon the surface of the 
liquid, its temperature must vary with that pressure. 
This is shown by placing a vessel of hot, but not 
boiling water under the receiver of an air pump, and 
exhausting the air. The water begins to boil as 
soon as the pressure upon its surface is less than the 
elasticity of the vapour. 

47. By removing the pressure altogether, liquids 
in genera], according to Robinson, boil at 140° F. 
(77.8° C.) lower than in the open air. The heat of 
the hand will boil water in the vacuum of the com- 
mon pulse glass, and ether will boil in it at the tem- 
perature of freezing mercury. By increasing the 
pressure upon the surface, we increase the tempera- 
ture of the boiling point of liquids. In the following 
table the first and third columns indicate the pres- 
sure, that of the atmosphere being unity, and the 
second and fourth the temperature at which water 
boils when exposed to it. 

TABLE. 



1 


212° 


5 


307° 


2 


250.52 


10 


358.8S 


4 


293.72 


20 


418.46 


8 


341.78 


40 


486.59 


6 


382.48 


50 


510.60 



48. That liquids render caloric latent in becoming 
aeriform, is shown by the same proofs as in the 
liquefaction of solids. As solids cannot be heated 

4 



38 ELEMENTS OF CHEMISTRY. 

beyond their melting point, so liquids cannot be heat- 
ed beyond their boiling point. All the additional 
heat that passes into the liquid is employed in con- 
verting it into vapour, the temperature of which is, 
notwithstanding, precisely that of the liquid itself. 

If we condense a given weight of steam, by pass- 
ing it in a spiral metallic tube (as the worm of a 
common still, for instance) through water, we shall 
find that it will heat about ten times its weight of 
water from 32° to 145°, that is, the quantity of calo- 
ric given out by aqueous vapour in being condensed, 
is sufficient to heat ten times its own weight of wa- 
ter 113 degrees, and it may therefore be stated to be 
1212°. This is found to hold true at whatever tem- 
perature the steam is formed; that is, steam gene- 
rated under the pressure of 50 atmospheres and in- 
dicating a temperature of 510.6°, gives out no more 
heat in condensing than an equal weight of steam 
formed at the common pressure, and indicating, 
therefore, the ordinary boiling point of 212°. But 
as the sensible temperature of the steam in the one 
case is 478°, and in the other 180° above 32°; 478° 
of the heat communicated to the water in the former 
case, and 180° of that communicated in the latter, 
must be regarded as being furnished by the sensible 
heat of the steam, and the latent heat in the former 
case must therefore have been 652°, and in the latter 
950°. 

49. The same facts have been ascertained in re- 
spect to other vapours, and we thus arrive at the 
remarkable law that the sum of the sensible and 
latent heat of a vapour, at whatever temperature 
and under whatever pressure it is formed, is a con- 
stant quantity. 

50. Excepting, then, that at the higher tempera- 
ture more heat is lost from the apparatus by conduc- 
tion and radiation, no more caloric is required to 
generate a given weight of vapour at 510° than at 



LIQUEF ACTION OF GASES. 39 

212°, while the elasticity or value as a mechanical 
power, of the steam at 510°, is fifty times that of 
steam formed at the ordinary pressure. 

51. The following table exhibits the boiling point 
of several liquids, the latent heat of their vapours, 
and the increase of volume of each fluid in becoming 
vapour. 



Water 


Sp. Gr. 

1.000 


Boiling- Latent heat 
point. of vapour. 

212°F. 1000° 


Sp. Gr. of 
vapour. 

.625 


Increase 
of volume. 

1689. 


Alcohol 


.813 


173.5 457 


1.601 


493.5 


Ether 


.736 


100. 312.9 


2.581 


212.18 


Oil of Turpent 


ine .86 


316. 183.8 


4.764 


192.15 


52. When 


liquids 


which mingle 


in all 


propor- 



tions, as alcohol and water, are of unequal volatility, 
we can separate them by exposing the mixture to a 
temperature below that at which the least volatile 
boils, and collecting and condensing the vapour of 
the other. This process of distillation is chiefly used 
in obtaining alcohol from fermented liquors, and their 
essential oils from plants which have been previous- 
ly macerated with water. 

53. Liquefaction of Gases. — As the state in which 
bodies exist, is found to depend upon their tempera- 
ture, it is evident that there must be a degree of cold 
in which all fluids become solid, and all gases fluid or 
solid ; while on the other hand heat will liquefy or vo- 
latilize all solids. There are no solids which chemists 
have not been able to melt or volatilize ; alcohol is 
the only substance, liquid at common temperatures, 
which has not been frozen. Many of the perma- 
nent gases have been liquefied by cold and pressure, 
and one of them, namely, carbonic acid, has been 
solidified. This liquefaction of the gases was first 
performed by Faraday, by disengaging them from 
their combinations, under a pressure, and in a space 
that did not allow of their assuming the gaseous 
form. For this purpose the materials for producing 



40 



ELEMENTS OF CHEMISTRY. 



the gas are put into a strong glass tube which is 
afterwards hermetically sealed, and bent in the mid- 
dle in an obtuse angle. The gas is generated by the 
application of heat, if necessary, and when the pres- 
sure becomes sufficiently great, is condensed into a 
liquid form and collects in the free end of the tube. 
The great elasticity of the condensed gas, (equal in 
some cases to a pressure of 50 atmospheres,) renders 
some of these experiments extremely dangerous. 

54. Penetration of Gases. — The mechanical ac- 
tion of gaseous fluids upon each other is regulated 
by peculiar laws. When two liquids of unequal 
density are placed in the same vessel, they do not 
mingle, unless in consequence of chemical affinity, 
but the heavier remains at the bottom. If, how- 
ever, two vessels*, communicating by their necks be 
placed the one above the other, and the one be filled 
with hydrogen gas, and the other with carbonic acid 
gas, which is twenty-two times heavier than hydro- 
gen and has no affinity for it, the gases will be found 
after a short interval to be equally diffused through- 
out the whole space. This experiment proves that 
the presence of a substratum of gas twenty-two times 
heavier than itself, is no obstacle to the diffusion of 
the hydrogen through the lower flask as completely 
as if it had been empty. When the two gases are in 
contact, the particles of each gas insinuate themselves 
between those of the other until they are perfectly 
mingled. It has been, therefore, inferred by Dalton, 
that the particles of gas, although highly repulsive 
of each other, do not repel those of a different kind. 
This does not seem, however, to be a necessary in- 
ference; and the mutual penetration of gases is pro- 
bably a consequence of that disturbance of their 
equilibrium, which must take place when the two 
vessels are made to communicate. We know that 
the particles of other bodies freely penetrate between 
those of water, and when it is recollected that the 



PENETRATION OF GASES. 41 

particles of aqueous vapour are twelve times more 
distant from each other than those of the liquid, it is 
evident that the slightest disturbance in the equili- 
brium of a gas so constituted, must be propagated 
throughout its whole volume, and that it can only be 
restored by the equal diffusion of the similar parti- 
cles. This, in the case of gases, whose corpuscles 
differ in respect to magnitude and weight, must pro- 
duce the mutual penetration which is characteristic 
of elastic fluids. 

55. If the two vessels in the above experiment be 
separated by a plug of plaister of paris, it will not 
prevent the mutual penetration of the gases. If a 
bottle containing hydrogen gas have its mouth closed 
by a sheet of bladder, or Indian rubber, the hydrogen 
will escape through it, and the external air will at 
the same time pass into the bottle: yet the hydrogen 
will pass through so much more rapidly than the 
atmospheric air that the membrane will be forced in, 
and will finally be torn by the external pressure. 

Experiments have proved that the velocity, with 
which this diffusion takes place, is inversely as the 
square root of the specific gravity of the gas, and 
that if the vessel be surrounded by a vacuum the 
several gases will pass through the porous stopper 
of plaister in times proportioned to the same law. 
By the following table it will be seen that in the 
time in which 100 measures (the diffusion volume) 
of atmospheric air, pass through a porous plug, 3S3 
volumes of hydrogen, 130 of ammonia, &c. will 
escape. 





Sp. Or. 


Sp. Or. 


Diffusion volume. 


Hydrogen, 


.068S 


.2623 


3S3 


xlmmonia, 


.5898 


.7681 


130 


Air, 


1. 


1. 


100 


Carbonic Acid, 


1.5239 


1.2345 


81 


Chlorine, 


2.4700 


1.5716 


64 



56. This law does not hold when the gases are in 

4* 



42 ELEMENTS OF CHEMISTRY. 

contact with moist membranes or Indian rubber; for 
in these cases the gases which are most easily lique- 
fied are transmitted in the greatest quantity, and it 
seems necessary to suppose that they are condensed 
by contact with the membrane and that they pass 
through in the fluid state. 

57. In perfectly elastic fluids, the density varies 
as the pressure. The gas which under a pressure of 
one pound on th& square inch occupies two cubic 
feet, will be compressed into half the space by double 
the pressure. This law is known by the name of 
Mariotte's law. There is reason to believe, that 
under very great pressure, and at temperatures much 
above the boiling point of their respective fluids, it 
does not hold good. Under very powerful pressure 
fluids may be made to assume the gaseous form, in 
a space but little greater than their bulk when liquid. 
Ether becomes a gas at 320° in twice the space it be- 
fore occupied ; alcohol at 404° becomes gaseous in a 
space only three times greater than its liquid volume; 
and water at773°isa gas with four timesits fluid bulk. 
In all these cases the elastic force of the vapour is 
less than the theory of elastic fluids would lead us 
to suppose. 

As a general rule gases expand far more than 
liquids, yet carbonic acid, which is only known to 
us in its liquid form under very great pressure, ex- 
pands one per cent, of its bulk for every degree of 
Fahrenheit, which is four times the rate of the ex- 
pansion of air. These facts render it probable that 
under extreme circumstances of heat and pressure, 
there are states intermediate between a liquid and a 
perfectly elastic gas, analogous to the viscidity of 
tenacious fluids, and the flexibility of soft solids. 

58. Incandescence. — When a solid substance, such 
as iron, is heated to a certain temperature, it begins 
to emit light, in conjunction with heat. Luminous 
hot bodies are said to be incandescent ; and the tern- 






FLAME. 43 

perature at which solids become incandescent in the 
dark is between 600° and 700° F. They do not be- 
come luminous in broad day light till about 1000° F. 
The colour of incandescent bodies varies with the 
temperature. The lowest degree is an obscure red, 
which becomes more and more vivid till it acquires 
a full red glow, which gradually becomes white, 
shining with increased brilliancy as the heat aug- 
ments. Liquids and gases become incandescent 
Avhen strongly heated, but a very high tempera- 
ture is required to render a gas luminous, higher 
than is sufficient for heating a solid body even to 
whiteness. The most intense incandescence known, 
is that produced by placing a fragment of lime, or of 
the other earths, in the jet of flame from an oxyhy- 
drogen blow pipe. So powerful is the light thus pro- 
duced by a piece of lime no larger than a filbert, that 
it has cast a shadow at the distance of a quarter of 
a mile. 

59. Flame. — The different kinds of flame are in- 
candescent gas. That this is the case is evident from 
the examination of the flame of an ordinary lamp. 
If the combustible used be alcohol, a flame of great 
heating power but of a feeble light is emitted, be- 
cause the products of the combustion are gaseous. In 
the oil lamp the lower part of the flame emits a pale 
blue light, for there the combustion is at once per- 
fect. Higher up, where the combustible material is 
in excess, the flame is of a brilliant yellow, passing 
into an intense white light, and surrounded by a pale 
yellow flame. The dark interior of the flame is the 
column of inflammable vapour which rises from the 
wick, and of which only the external particles are 
in contact with the air so as to take fire. The flame 
is therefore a hollow cone, of which the paler exter- 
nal portion contains only gaseous particles, while the 
white light of the interior stratum is owing to the 



44 ELEMENTS OF CHEMISTRY. 

solid particles of carbon, which are heated to bril- 
liant incandescence before they are completely 
burned. 

60. Transmission of Heat. — If we apply the 
hand to a number of different bodies exposed in the 
same situation, we shall find them to indicate very 
unequal degrees of warmth, while a thermometer 
will probably exhibit the same temperature in them 
all. 

If we dip into a vessel of boiling water the ends 
of wooden, leaden, and copper rods, of equal length 
and thickness, we shall find the copper rod to be- 
come hot sooner than that of lead, and this much 
sooner than the rod of wood. 

These simple experiments acquaint us with the 
fact that caloric passes with different degrees of ve- 
locity through bodies; which are hence divided into 
conductors and non-conductors of heat. The metals 
belong to the former, and wood, glass, and char- 
coal, to the latter class. Fine down, silk, wool, and 
cotton, are the slowest conductors of heat among 
solid bodies. 

The following table, by Despretz, shows the rela- 
tive conducting power of the substances mention- 
ed :— 



Gold, 


1000 


Tin, 


303.9 


Silver, 


973 


Lead, 


179.6 


Copper, 


898.2 


Marble, 


23.6 


Platinum, 


381 


Porcelain, 


12,2 


Iron, 


374.3 


Clay, 


11.4 


Zinc, 


363 







61. What has been said of the constitution of 
liquids, and the expansive effect of heat, has pre- 
pared the student for understanding the manner in 
which fluids are heated. When the heat is applied 
at the bottom of a vessel containing any fluid, the 
particles first heated expand, and, thus becoming 



TRANSMISSION OF HEAT. 45 

specifically lighter than those around them, rise to 
the surface. They are replaced by other cold parti- 
cles, and thus the whole mass of the fluid is brought 
in succession to the part where the heat is applied, 
and heated there. This circulation of particles is 
readily shown by adding fragments of an insoluble 
substance of a specific gravity nearly equal to that 
of the fluid. These will be carried along with the 
ascending and descending currents, and exhibit the 
circulation very clearly. 

62. It is evident from the constitution of gases that 
they must be heated by means of a similar circula- 
tion, when the heat is applied beneath. The only 
method of ascertaining the actual conducting power 
of fluids and gases, must, therefore be, to apply the 
heat at the upper surface; as, in this case, all that is 
communicated to the particles below must be in vir- 
tue of this power. Careful experiments have ascer- 
tained that fluids, with the exception of the fluid 
metal, mercury, are very imperfect conductors. Dr. 
Trail placed a thermometer horizontally in a small 
vessel of dried wood, and covered the bulb to the 
depth of half an inch with various liquids; he then 
brought an iron cylinder an inch in diameter, and 
heated to 212° F., into contact with the surface of 
the fluid, and observed the time required to raise the 
thermometer 3° F. 

In mercury this effect was produced in 0' 15". 

In water . . . in 7' 5". 

In alcohol ... in 15' 40". 

The slowness with which water is heated from 
above is strikingly shown by setting fire to a small 
quantity of ether on its surface, in a tin or glass 
vessel. An equal quantity of water may be boiled 
by being placed over the flame r while that beneath 
is scarcely rendered warm. 

The extreme mobility of the particles of a gas ren- 



46 ELEMENTS OF CHEMISTRY. 

ders it difficult to ascertain their power of conduc- 
tion. It is certain, however, that it is exceedingly 
imperfect. 

63. Radiant Heat. — We have thus seen that all 
bodies unequally heated, which are placed in con- 
tact with each other, tend to become of the same 
temperature. The same effect takes place at sensi- 
ble distances. If a heated iron ball be suspended in 
an apartment, the heat will be diffused from it in all 
directions, and thermometers, at equal distances on 
every side, will be instantly and equally affected. 
The heat in this instance is said to be radiated, and 
is called radiant heat. It is diffused in the same 
manner as light is radiated, by the emanation of par- 
ticles in all directions in right lines; for the effect 
upon the thermometer instantly ceases when any 
object is interposed between it and the ball. It is 
not communicated by the conducting power of the 
air, for it passes downwards as freely as upwards, 
and it does not heat the air through which it passes, 
neither is its direction changed by a current of wind. 

If a plane metallic mirror be placed opposite the 
heated ball, it will be found that the rays of heat 
which impinge against it are reflected, and that the 
law of reflection is the same as in the case of light, 
namely, the angle of incidence is equal to the angle 
of reflection. If smooth planes of different sub- 
stances, such as glass, polished metal, wood, &c. are 
placed at equal distances from the ball, it will be 
found that they differ in their power of reflection. It 
is evident that all the rays which are not reflected 
must be transmitted or absorbed, and we, therefore, 
infer that those bodies which are not good reflectors 
must either absorb the rays and become heated, or 
transmit them and be diathermanous, that is, trans- 
parent as regards heat. 

Most substances, it is found by experiment, absorb 



i 



RADIANT HEAT. 47 

the rays and become heated in the inverse ratio of 
their reflecting power. Few substances besides the 
gases transmit caloric without absorption. 

64. Radiant heat must, it is evident, be capable of 
being converged to a focus when reflected from a 
concave surface, for this property is a consequence 
of the law of reflection above stated. 

The most convenient apparatus for demonstrating 
this, and for ascertaining the radiating power of sub- 
stances, is two concave metallic mirrors of the dia- 
meter of 12 or 18 inches, and a focal distance of 4 or 
6 inches, mounted on stands. The mirrors are placed 
at a distance of 10 or 12 feet from each other, and 
one of the balls of a differential thermometer is placed 
in one focus, and the substance to be experimented 
on in the other. All the rays emanating from the 
substance that strike the mirror which is nearest to 
it, are reflected in parallel lines to the other mirror, 
and there converged to its focus. A heated ball in 
one focus will instantly raise the thermometer in the 
other, and that this is owing to the reflection of the 
mirrors, may be proved by intercepting the direct 
rays from the ball to the thermometer, which will 
not affect the instrument; while it is instantly lower- 
ed by placing a glass plate between it and its nearest 
mirror, so as to prevent the passage of the reflected 
rays. 

65. A convenient way of ascertaining the radia- 
ting power of bodies is to place a cubic vessel of pol- 
ished tin, filled with hot water, in one focus, and 
then to observe the effect upon the differential thermo- 
meter in the other, when the side of the vessel next 
to the mirror is coated with different substances. 
The numbers in the following table represent the 
rise in the thermometer when exposed to the influ- 
ence of the respective radiating substances, for equal 
intervals of time, and, therefore, exhibit their relative 
radiating power: 



48 



ELEMENTS OF CHEMISTRY. 



Lampblack, water (by estimate) 

Writing paper 

Resin 

Crown glass 

Indian ink 

Ice 

Minium, isinglass 

Plumbago . 



100 
98 
96 
90 
88 
85 
80 
75 
45 
20 
19 
15 
12 



Tarnished lead 

Mercury- 
Clean lead 

Iron, polished 

Sheet tin, gold, silver, copper 

66. In general the more polished and smooth a 
surface, the more feeble the radiation. Organic sub- 
stances are generally good, and the metals very bad, 
radiators, although the power of the latter is much 
increased by making their surface rough. Heat is 
radiated altogether from the surfaces of bodies, and 
although the radiating power of a very thin film of 
jelly was increased by an additional layer, it reached 
its maximum when the film had attained the thick- 
ness of the 1000th part of an inch. 

That the absorbent power of surfaces is precisely 
proportional to their radiating power, may be proved 
by means of a large differential thermometer, the 
bulbs of which are hemispherical chambers, of con- 
siderable size, with the flattened surfaces towards 
each other; midway between them is placed a glass 
vessel with equal plane surfaces, facing those of the 
bulbs. One of the sides of the vessel and of the bulb 
is left uncovered, and the other is coated with a film 
of some feebly radiating substance. The vessel is 
then filled with hot water, and, when the coated sides 
are turned towards each other, the liquid in the tube 
of the thermometer is instantly affected, and recedes 
from that bulb which is the best radiator and absor- 
ber. When the coated side of the vessel is turned 



RADIANT HEAT. 



49 



to the uncoated bulb, the worse radiating to the better 
absorbing surface, the liquid in the tube is stationary, 
thus establishing the exact equality of the absorbing 
and radiating powers. 

67. If a ball of ice be placed in the focus of one of 
the mirrors, the thermometer in the other will in that 
case become the greater radiating, because it is the 
hotter body, and will indicate a loss of heat. 

Pictet placed the mirrors sixty-nine feet apart, and 
ascertained that no perceptible interval of time was 
occupied by caloric in traversing that space. 

These experiments must be performed with me- 
tallic mirrors, for glass mirrors absorb so much of the 
caloric as to produce a very slight effect upon the 
thermometer. 

Leslie determined the reflecting power of several 
bodies as follows: 

Brass ..... 

Silver • 

Tin foil 

Block tin . 

Steel 

Lead .... 

Tin foil softened with mercury 

Glass .... 

Do. coated with wax or oil 

68. The power of bodies to intercept radiant heat 
is influenced by the conducting power of their par- 
ticles, and the absorbing power of their surfaces 
jointly, as is shown by the following experiment. 
When two panes of glass, each coated on one side 
with tin foil, were used as a screen, they intercepted 
all the heat when the coated surfaces were the exter- 
nal ones ; when these surfaces were placed together, 
the effect on the thermometer was to reduce it from 
100° to 18°. 

In this experiment, the radiant heat, which was 
altogether reflected by the tin foil, when placed ex- 

5 



. 


90 




85 


. 


SO 




70 


. 


60 




10 


. 


10 




5 



50 



ELEMENTS OF CHEMISTRY. 



ternally, was, after having been absorbed by the 
glass, conducted by the tin when this metal was sur- 
rounded by glass. 

69. The law of cooling. — Sir Isaac Newton sup- 
posed the law of cooling to be such, that the heat 
lost by hot bodies in equal intervals of time, was a 
constant fraction of the excess at the beginning of 
each interval. Thus if a body heated 100 degrees 
above the surrounding temperature, were to lose 
■^ of that excess, in 10° in the first second, it would 
lose -jL of the remaining excess of 90° or 9° in the 
next second, and so on. It is now known that this 
is only an approximation to the law of cooling, and 
that its quickness, so far as it depends on the tempera- 
ture of the hot body, increases as the terms of a geo- 
metrical progression diminished by a constant num- 
ber *, when the temperature of the hot body increases 
in arithmetical progression. 

70. Transmission of radiant heat through solids. 
— It is evident, as has been said, that when radiant 
heat impinges upon a surface, it must either be re- 
flected, absorbed, or transmitted. The fact that the 
absorbing power of most solid bodies, is in the in- 
verse ratio of their reflecting power, proves that few 
solids are diathermanous. The metals are absolute- 
ly opaque to radiant heat. 

The heat of the sun passes with its light through 
most transparent bodies without loss. But of the 
heat of incandescent bodies, a portion only, (which 
increases with the temperature) passes through solid 
media, such as screens. Non-luminous radiant heat 
is also transmitted by bodies in various proportions; 
and it is found that this property of diathermancy is 
altogether independent of transparency. 

71. By means of instruments of extreme sensibij 
lity, Melloni ascertained the laws which regulate the 
transmission of radiant heat through various bodies. 

The following table exhibits the results obtained 









TRANSMISSION OF RADIANT HEAT. 51 

by transmitting radiant heat from various sources, 
through plates l-10th of an inch in thickness of the 
several bodies mentioned. Out of one hundred rays 
emanating from the source, these were transmitted 
as follows: 





Flame of 


Ignited 


Copper. 


Copper. 




a lamp. 


Platinum. 


734° 


212° 


Rock Salt, 


92 


92 


92 


92 


Fluor Spar 5 


78 


69 


42 


33 


Calcareous Spar, 


39 


28 


6 





Plate Glass, 


39 


24 


6 





Gypsum, 


14 


5 








Alum, 


9 


2 








Ice, - 


6 











Sulphate of Copper, 















It thus appears that heat of all temperatures pass- 
es freely through rock salt, which is to radiant heat 
what perfectly clear glass is to light; while on the 
other hand alum and ice, which are nearly transpa- 
rent, arrest nearly the whole of the heat, and sul- 
phate of copper is absolutely impermeable to it. It 
is also evident that the penetrating power of heat 
increases with the temperature. Plate glass, which 
allows nearly all the solar heat to pass, intercepts 61 
per cent, of the rays from a lamp, and all the rays 
from copper at 212°. A plate of alum intercepts 91 
per cent, of the direct rays from the lamp, while a 
second plate intercepts only 10 per cent, of those 
which have passed through the first. Calcareous 
spar, which intercepts 61 per cent, of the direct rays, 
intercepts 9 per cent, of the heat which had passed 
through alum, and 11 per cent, of that which had 
passed through gypsum. 

On the other hand, a green tourmaline intercepts 
82 per cent, of the direct rays, 99 per cent, of those 
which had passed through alum, and 70 per cent, of 
those which had passed through black glass. 

72. If the rays from a lamp be made to pass 
through a prism of rock salt, a luminous spectrum 



52 ELEMENTS OF CHEMISTRY. 

will be formed, and it is found that there is a per- 
fectly distinct spectrum of radiant heat accompanying 
it, the most refrangible rays of which are near the 
middle of the luminous spectrum, while the least re- 
frangible ones extend far beyond the least refrangible 
luminous rays. Rock salt allows all the rays to pass 
with equal facility; a plate of alum intercepts all but 
the least refrangible rays, while a plate of rock salt 
covered with soot, allows only those most refrangi- 
ble to pass. It thus appears that the action of dif- 
ferent media upon radiant heat is precisely similar 
to that of transparent coloured bodies upon light, 
and that heat like light consists of rays of unequal 
refrangibility, which may be separated by the spec- 
trum, and are absorbed and transmitted in various 
proportions by various bodies. 



CHAPTER III. 

LIGHT. 

73. The close resemblance between light and heat, 
and the influence which light exerts over chemical 
phenomena, render some notice of its properties ne- 
cessary in this introduction. 

Light is emitted in straight lines, in all directions, 
by a luminous body. 

The quantity of light which falls on any given sur- 
face, is therefore in the inverse ratio of the square 
of the distance from the luminous point. 

Light is communicated with inconceivable ra- 
pidity. It passes over 195,000 miles in a second, 
and is eight minutes in traveling from the sun to 
the earth. 

When light falls upon any body it may, like ra- 
diant heat, be reflected, transmitted, or absorbed. 



REFRACTION. 53 

74. Reflection. — The reflection of light takes place 
at the surface of bodies, which must be smooth and 
polished. Liquids and polished metals are the best 
reflectors of light; when light is reflected, the inci- 
dent and reflected rays are in the same plane, and 
that plane is perpendicular to the reflecting surface. 
The angles formed by these rays with a line perpen- 
dicular to the reflecting surface, are called the angles 
of incidence and reflection, and these angles are 
always equal to each other. It is in virtue of this 
property that light is converged to the focus of a 
concave mirror. Light is not reflected by gaseous 
bodies, but it is reflected by the clouds and other 
aqueous particles floating in the atmosphere. Bodies 
which reflect all the light that falls upon them are 
called opaque. 

75. Refraction. — Transparent bodies are those 
through which light passes freely in a straight line. 
When it passes from one medium into another of a 
different density, or into a denser or rarer part of the 
same medium; it undergoes a change of direction at 
the plane of junction of the two media, unless the 
ray is perpendicular to that plane. This change is 
such that in passing from the rarer into the denser 
medium, the ray is always bent towards a line drawn 
perpendicular to the plane that separates the two 
densities, and vice versa. In this case the ray of 
light is said to be refracted. 

The more dense a substance becomes, the greater 
is its power of refracting light. Inflammable bodies 
have a refractive power from two to seven times great- 
er than incombustible substances of equal density. 

The refractive power of water is shown by putting 
a piece of money in the bottom of a basin and then 
placing it so as to be barely hid by the rim of the 
vessel; if the basin be then filled with water, the 
piece of coin will be fully visible. 

76. Index of Refraction. — The direction of the 

5* 



54 ELEMENTS OF CHEMISTRY. 

incident and refracted rays is always in a plane per- 
pendicular to the common surface of the media, and 
whatever angle the incident ray makes with a line 
drawn perpendicular to that surface, it bears a con- 
stant relation to the angle between the same perpen- 
dicular and the refracted ray. This relation is such 
that the sine of the angle of incidence and that of 
the angle of refraction are in a constant ratio for the 
same medium. 

This remarkable law furnishes us with a very con- 
cise mode of expressing and comparing the refractive 
powers of bodies. The sine of the refracted ray 
being taken as unity, the sine of the incident ray is 
a constant quantity, and forms what is called the in- 
dex of refraction. Thus the index of refraction for 
water is 1.336, and for the diamond 2.755. 

It is the refraction of light in passing through glass 
plates with convex surfaces that enables us to con- 
verge it to a focus and thereby to construct opti- 
cal instruments of great magnifying power. This 
branch of the investigation does not however belong 
to chemistry. 

77. Composition of Light. — When the light of the 
sun is received upon one of the sides of a plane tri- 
angular prism of glass, an image or spectrum of 
coloured light will be formed on the wall of the room 
in which the experiment is made. This spectrum 
consists of red, orange, yellow, green, blue, indigo, 
and violet, in the order enumerated ; the red being 
the colour which suffers the least refraction. If this 
spectrum be received upon the surface of a large 
lens, the light will be converged and a round spot of 
white light be formed in the focus. It is therefore 
evident that the white rays are a compound light, 
formed by the union of the colours of the solar 
spectrum. 

78. If a piece of coloured glass be interposed be- 
tween the prism and the spectrum, it will absorb 



CHEMICAL RAYS. 55 

some of the rays and transmit the others. By means 
of this absorption it has been proved by Sir David 
Brewster, that the solar ray is actually resolved into 
red, yellow, and blue light; and that these colours 
are all present with various degrees of intensity, in 
every part of the spectrum. They are each most 
intense near the middle of their apparent place in 
the spectrum, and diminish gradually in intensity 
from that point. The other colours, orange, green, 
indigo, and violet, are formed by the union of the 
adjacent primitive colours. 

79. Calorific Rays, — It is probable that there are 
rays of light to which the eye is insensible, in the 
same manner as the ear is insensible to certain 
sounds. For it is ascertained that rays, which do 
not affect the eye, exist beyond each extremity of 
the solar spectrum. Sir William Herschell examined 
the heating power of the several colours of the spec- 
trum, and found that it was least at the violet end, 
and gradually increasing, became greatest at the ex- 
tremity of the red: by placing the thermometer be- 
yond the red end of the spectrum, he found that it 
continued to rise, and that the most intense heating 
power was always beyond the red ray, where there 
was no light at all. 

80. Chemical Rays. — It is well known that the 
light of the sun destroys certain colours, and revives 
certain metals from their oxides, besides producing 
other chemical changes. There is a substance called 
chloride of silver, which is white when first prepared, 
and slowly becomes darkened by exposure to the 
diffused light of day; but blackens in a few minutes 
in the direct rays of the sun. Upon exposing this 
substance to the solar spectrum, it is found that the 
red, orange, and yellow, produced no effect; in the 
green it is slowly blackened; the effect increases in 
approaching the violet end, and is greatest at a point 
beyond the spectrum. 



56 ELEMENTS OF CHEMISTRY, 

We thus learn that there are rays in the spectrum 
which do not affect the eye ; that some of these 
which are less susceptible of refraction, or as it is 
termed, are less refrangible than the least refrangible 
of the visible rays, are calorific rays, and others which 
are more refrangible than the violet, are chemical 
rays. The calorific rays appear to be diffused over 
the least refrangible, and the chemical rays over the 
most refrangible end of the spectrum, and they in- 
crease in intensity as they approach their respective 
points of maximum. 

Sir John Herschel has discovered that the solar 
spectrum imparts a tint corresponding to that of the 
light, upon paper properly prepared with chloride of 
silver. 

81. The Daguerreotype. — The most surprising 
effect of the chemical rays is that produced in the pro- 
cess of Daguerre for fixing the images of the Camera 
Obscura. This is done upon plates of silvered 
copper. They are covered with a fine film of iodine 
by exposure to its vapour, and are then placed 
for a few seconds in the focus of a camera obscura. 
When taken out there is no visible image impressed, 
but a short exposure to the vapour of mercury brings 
out the magical picture with a distinctness, brillian- 
cy, and softness, which no language can describe. 
The theory of this process is not yet understood, but 
the effect is owing to the chemical rays; for a red, 
or orange light produce a feeble effect ; green objects 
are scarcely defined, while a deep blue is more pow- 
erful than a brilliant white light. 

82. Colours of Bodies. — The colours of bodies 
are supposed to be owing to their absorbing some of 
the rays of the spectrum, and to their reflecting those 
which give them their colour. In proof of this, 
bodies take the colour of the light to which they are 
exposed. White bodies reflect and black bodies ab- 



PHOSPHORESCENCE. 57 

sorb all the rays. The solar ray being a compound 
of light and heat, or a union of luminous and calo- 
rific rays, bodies which are exposed to it become 
heated. Dark coloured substances acquire a higher 
temperature by exposure to the sun's light than white 
bodies. 

83. Light produced by combustion and high de- 
grees of heat, has the same properties in respect to 
chemical agency, refraction, and reflection, as solar 
light. It differs in respect to its composition, accord- 
ing to the substance from which it emanates. The 
light from the flame of an alcoholic solution of stron- 
tia, is red ; — the flame of a similar solution of boracic 
acid, or of the salts of copper, is green ; that from one 
of soda, is yellow. A portion of the heat which is 
in union with the light of burning bodies, is in the 
state of ordinary radiant heat, and will not pass with 
the light through a thick plate of glass, while another 
portion appears to be united with the light as in 
the solar ray, and is capable of refraction along 
with it. 

84. Phosphorescence. — Many bodies by exposure 
to the solar ray absorb light, and emit it again when 
brought into a dark place. Canton's phosphorus, 
which is made by heating to a red heat, in a covered 
crucible, a mixture of three parts of calcined oyster 
shells, and one of flowers of sulphur, possesses this 
property. This power of emitting light in the dark, 
is called phosphorescence. It is possessed by many 
insects and marine animals and by certain vegetables 
in the living state. Light is also emitted during the 
processes of crystallization, and of putrefaction. 



ELEMENTS OF CHEMISTRY. 



CHAPTER IV. 



ELECTRICITY. 



85. In speaking of the constitution of firm solids 
and crystals, it was stated that we must conceive their 
particles to be endued with points of attraction and 
repulsion. This property of polarity, as it is termed, 
is exhibited by various bodies under different cir- 
cumstances. 

86. Magnetism. — There is a peculiar ore of iron, 
which has been known for ages, on account of its 
property of attracting pieces of iron. This stone is 
calied the magnet, and its properties may be com- 
municated, by several different methods, to metallic 
iron. 

The best form of the iron for these experiments is 
that of a straight bar or needle. It will be found 
that a bar of iron to which the power of attracting 
)ther pieces of iron has been communicated, pos- 
sesses the following properties. 

S7. If it is poised on its centre so as to move freely 
in a horizontal plane, it will remain, when at rest, 
in a nearly north and south direction; and the same 
end will always point in the same direction. The 
two ends of the magnetised bar, or magnet as it is 
called, are termed its poles, and are distinguished, 
according to the direction in which they point, as 
the north and south poles. 

88. If either pole of a magnetised bar, vibrating 
freely on its axis, be approached by the same pole of 
another magnet, they will repel each other; and if it 
be approached by the opposite pole they will attract 
each other. 

If two magnetised bars of equal magnitude and 
power, be placed together, the north pole of each, in 



ELECTRICITY FROM FRICTION. 59 

contact with the south pole of the other, their mag- 
netic force is neutralised, and they no longer possess 
the power of attracting iron. 

89. If a magnet be placed beneath a sheet of paste- 
board or paper, and iron filings be scattered over the 
paper, each particle will itself acquire magnetic po- 
larity, and they will arrange themselves in regularly 
curved lines around the poles of the large magnet 
beneath. 

The science which investigates these phenomena 
is called Magnetism. 

90. Electricity from Friction. — Attractive and 
repulsive forces, analogous to those of the magnet, 
may be developed in other bodies, by friction and 
various other means. 

91. If amber, resin, sulphur, and glass, for exam- 
ple, be rubbed with dry silk or cloth, they acquire 
the power of attracting light bodies; the property 
ceases after a while, but may be renewed at pleasure 
by the same means. 

After the light body has remained for a short time 
in contact with that which has been excited, as it is 
termed, by friction, the attractive force is changed in- 
to a repulsive one, and the body is driven off. 

92. Small balls of pith suspended by dry silken 
strings, are very convenient for the performance of 
these experiments. If a pith ball thus suspended, 
after being attracted and then repelled, have the ex- 
cited body again brought near it, it will be repelled, 
nor can they without external force be again brought 
in contact. If two pith balls be thus suspended from 
the same point, they will, after contact with the ex- 
cited body, not only be repelled by it, but they will 
repel each other. The more dry the atmosphere, the 
longer will these phenomena continue. 

93. If the balls instead of being suspended by a 
dry silken string, be attached to a wet string, or 
thread, or wire, none of these phenomena take place, 



60 ELEMENTS OF CHEMISTRY. 

except the original attraction of the excited body, 
and this ceases almost immediately. 

We thus learn that there are certain substances 
which dissipate, or carry off, or conduct the attrac- 
tive forces developed by friction. These substances 
are said to be conductors, and those which do not 
possess this power, are called non-conductors of this 
attractive force. These attractive and repulsive 
forces were first observed in amber, or electron, as 
this mineral was called by the Greeks. They are 
therefore called electrical forces, and the science 
which investigates their effects is called Electricity. 

94. A conducting body may have the power of 
electrical attraction and repulsion imparted to it, pro- 
vided it be surrounded by non-conductors, in which 
case it is said to be insulated. The friction of two 
insulated conductors will excite electricity. A con- 
venient way of insulating a conducting body, is to 
place it on a support of glass or resin. 

If a pith ball, suspended by a non-conducting string, 
be brought into contact with a roll of excited resin 
or sealing wax, the power of attraction and repul- 
sion will be communicated to it, and it is said to 
have become charged. 

95. If we excite a tube or rod of glass, it will com- 
municate its charge to an insulated pith ball, in the 
same manner as resin, first attracting and then re- 
pelling it. 

But if the excited glass tube be brought near the 
pith ball, which has been charged from an excited 
piece of resin, instead of repelling it, it attracts it; 
and in like manner, excited resin attracts the pith 
ball which has been charged by excited glass. Pith 
balls that have been charged, the one by glass and 
the other by resin, also attract each other. 

It thus appears that while glass and resin repel 
the bodies to which they have imparted their own 
electricity, they each attract the bodies that have 



THEORY OF ELECTRICITY. 61 

been charged J^y the other. We therefore infer, that 
there are two kinds of electricity, each of which re- 
pels its own kind and attracts the other. The elec- 
tricity developed in glass, is called vitreous or posi- 
tive, and that in amber and resin, resinous or nega- 
tive electricity. 

96. Electricity from Induction. — Let a small 
metallic cylinder, one or two inches in diameter, and 
six or seven iches long, terminating in hemispherical 
ends, be insulated by supporting it on a glass rod. 
Let two pith balls be suspended by thread or wire, 
from each end of this cylinder. If an excited rod of 
glass or sealing wax be brought near it, the balls at 
each end will diverge from mutual repulsion, show- 
ing that electrical forces have been developed in the 
cylinder, by the mere approach of an excited body. 
If this body be withdrawn, the balls coalesce, prov- 
ing that the electrical forces have ceased to operate. 
If, while the balls are divergent, from the presence 
of the excited body, an excited glass rod be brought 
near them, it will be seen that one set will be at- 
tracted and the other repelled, proving that they are 
charged with different kinds of electricity. With 
whichever kind the body, the presence of which im- 
parted electricity to the cylinder, was charged, the 
balls nearest to it will be oppositely, and those far- 
thest from it, similarly electrified. 

If while the excited body be still near, the remote 
end of the cylinder be touched with the finger, the 
balls at that end will instantly collapse; if the ex- 
cited body be then removed, they will again diverge, 
and it will be found upon trial that both pairs are 
charged with the electricity of the pair at the end 
nearest the excited body. 

97. Theory of Electricity.— \x\ order to explain 
these phenomena, which are the fundamental facts of 
the science of electricity, it seems necessary to make 
the following supposition. 

6 



62 ELEMENTS OP CHEMISTRY. 

In consequence of the mutual attraction of the 
vitreous and resinous electricities, the state of rest 
or equilibrium of the electric fluids must be that of 
combination, and it is accordingly supposed, that in 
all bodies which do not exhibit electrical forces, the 
two fluids, which are universally diffused through- 
out nature, are in a state of combination. This com- 
bination may be disturbed in a variety of ways, and 
especially by friction. When two electric bodies 
are rubbed together, the vitreous electricity of both, 
accumulates in one, and the resinous in the other; 
when a body thus excited is surrounded by a non- 
conducting medium, such as a dry atmosphere, the 
electricity is not dissipated ; but it is found that a 
stratum of the medium immediately surrounding the 
excited body, becomes oppositely electrified, and that 
this is surrounded by another stratum similarly elec- 
trified with the body itself. 

98. This phenomenon is supposed to be caused by 
the electricity of the excited body disturbing the 
equilibrium of the surrounding medium, repelling its 
own kind, and attracting the opposite, so as to sur- 
round itself by an atmosphere of the latter within 
one of the former. This mode of disengaging or set- 
ting free the combined, or latent electricities of a 
body, is said to be by induction. 

As long as none of the free electricity of the ex- 
ternal stratum is carried off by the surrounding bo- 
dies, the mutual attraction of the two oppositely 
electrified strata keeps their electricities in tension, 
and that of the inner stratum does not exhibit any 
tendency to combine with the opposite electricity of 
the excited body. But if any portion of the electri- 
city of the outward stratum is carried off by conduc- 
tion, an equal portion of that of the inner stratum is 
left free, and combines with a portion of the electri- 
city of the excited body, which in this manner gra- 
dually parts with its charge. 



THE LEY DEN JAR. (33 

99. The application of these principles to the ex- 
planation of the experiment with the insulated cylin- 
der is obvious. The excited body being brought 
near one end, disturbs the electrical equilibrium, at- 
tracting the opposite electricity towards itself, and 
repelling its own kind to the extreme end of the cy- 
linder, as is shown by the opposite electrical condi- 
tions of the suspended pith balls. When the extreme 
end of the cylinder is touched with the finger, the 
electricity accumulated there is carried off, and if the 
excited body be then withdrawn from the other end, 
the opposite electricity there accumulated is diffused 
over the whole cylinder. 

100. In the common electrical machine, the elec- 
trical fluids are set free by the friction of the silk 
rubber against the glass plate or cylinder. The resin- 
ous electricity excited in the rubber is carried off 
by a communication with the ground, and the vitre- 
ous electricity developed in the cylinder is transfer- 
red to the prime conductor, where it accumulates. 
The discharge of the accumulated electricity from 
the conductor is accompanied with a crackling noise, 
and with a flash of light or spark, which is at times 
several inches long. 

101. The Leyden Jar. — The Leyden Jar is usu- 
ally a glass bottle with a wide mouth, coated on both 
sides to within a few inches of the top, with tin foil. 
A wire terminating at the top in a knob, and com- 
municating with the internal coating, by the other 
end, passes through the stopper of the bottle. When 
the knob of the jar is presented to the prime conduc- 
tor, it receives an electrical charge which is diffused 
over the inner coating. The electricity thus diffused 
disturbs the electrical equilibrium of the outer coat- 
ing, attracting the opposite electricity, and repelling 
that of the same kind with itself. 

. If the jar be insulated, and a brass knob, commu- 
nicating with the ground, be brought near the out- 



64 



ELEMENTS OF CHEMISTRY. 



side coating, it will be seen that a spark passes to the 
latter, whenever one passes from the prime conduc- 
tor to the knob of the jar. This spark is occasioned 
by the passage of the repelled electricity to the 
ground. The opposite electricities of the outer and 
inner coating maintain themselves in what may be 
called a forced equilibrium, by means of their mutual 
attraction. As long as a free passage is afforded to 
the repelled electricity of the outside of the jar, there 
does not appear to be any limit to the quantity of 
electricity, which may be thus accumulated, other 
than the strength of the glass to resist the passage 
of the fluid through its substance, and the distance of 
the coatings from each other over the top of the jar. 

When a communication is made between the 
outer and inner coating, by touching the former and 
the knob of the bottle with a metallic rod, the natural 
electrical equilibrium is restored, and the discharge 
of the jar is accompanied with a loud report, and a 
brilliant flash of light. 

102. There is evidently a strong affinity between 
the attractive forces thus developed, and those pos- 
sessed by the magnet. In both cases there appear 
to be two kinds of forces, and those bodies, or those 
portions of the same body, which are endued with 
the one, repel other bodies endued with it, and 
attract those endued with the opposite force. In 
both cases the tendency of these forces is to accu- 
mulate at the extremities of a body, especially if it 
be in the shape of a long ellipsoid or a needle. The 
attractive forces developed in the magnet are perma- 
nent, while those excited by the friction of electrics 
are fugitive. No such tendency as the north and 
south polarity of the magnet is observed in excited 
electrics, although by means of electricity powerful 
magnets may be made, and north and south polarity 
be communicated to metals not susceptible of perma- 
nent magnetism. 



ELECTRICITY FK031 CHEMICAL ACTION. 65 

103. Electricity from Chemical Action. — The 
natural equilibrium of the electric fluids may be dis- 
turbed, not only by friction and induction, but by 
chemical action. 

When a plate of zinc and a plate of copper are 
placed in a vessel of water, and the extremities 
which are not immersed, are connected by means of 
a wire or other perfect conductor, it will be found 
that a feeble current of vitreous electricity is trans- 
mitted through the conductor from the copper to the 
zinc plate, while a current of resinous electricity 
passes in an opposite direction. 

If the communication be interrupted, the currents 
cease entirely, but they continue as long as a pas- 
sage for the electric fluid is maintained. The force 
of this current is greatly increased by adding to the 
water a little sulphuric acid, which increases the 
chemical action to which this development of elec- 
tricity is owing. 

It is found that unless one of the metallic plates is 
more powerfully acted on by the fluid than the 
other, there is no disengagement of electricity, and 
it is also ascertained that the current of vitreous 
electricity always flows through the connecting wire, 
from the plate that is least acted on to the other. 

104. This branch of physical science is due to the 
genius of two celebrated Italian philosophers, Gal- 
vani, and Volta. An accidental occurrence led the 
former to a knowledge of its fundamental facts, and 
the science has received the name of Galvanism, to 
commemorate its discoverer. To the latter we are 
indebted for the discovery of these electric circuits, 
which are usually called Voltaic circles. The in- 
strument formed by connecting a number of simple 
circles, is called the voltaic, or galvanic battery. 

105. When a copper plate is partially immersed 
in dilute nitric acid, it is attacked by the acid, ni- 
trous acid vapours are disengaged, and the metal is 

6* 



66 ELEMENTS OF CHEMISTRY. 

oxidised and converted into a nitrate. If a plate of 
zinc be partially immersed in the same solution, it is 
also immediately oxidated and converted into a ni- 
trate. But if the two plates be connected by means 
of a wire, the action upon the copper plate ceases at 
once; the zinc alone is oxidated, and there is a dis- 
engagement of hydrogen gas at the surface of the 
copper plate. 

When zinc and copper plates, each cemented to a 
glass handle, are brought into contact, and the zinc 
is then applied to an electrical condenser, it is found 
to have acquired a positive or vitreous charge, and 
the copper in like manner is ascertained to have be- 
come negative or resinous. 

106. Voltaic Circles, — As it appears to be essen- 
tial to the disengagement of electricity that the chemi- 
cal action on the metallic surfaces should be of une- 
qual intensity, it is manifest why three elements are 
necessary to form one of these electrical, or, as they 
are called, voltaic circles. 

These may be either two perfect conductors and 
one imperfect one, as in the case just given, or one 
perfect conductor and two imperfect ones. A circle 
of the latter kind may be made by cementing a plate 
of zinc into a box, so as to form two separate cells, 
which are filled with liquids that act unequally upon 
the opposite surfaces of the metal; with a solution 
of salt, for example, in one cell, and with diluted 
nitric acid in the other. In this case the circuit must 
be completed by forming a communication between 
the liquids by means of a bent wire, and the current 
of vitreous electricity passes through the wire, from 
the liquid of the less chemical action to that having 
the greater. 

In all these cases the electrical current is set in 
motion by the decomposition of the water. Its oxy- 
gen unites with that metal which has the greater 
affinity for oxygen^ and its hydrogen is disengaged 



VOLTAIC CIRCLES. 67 

at the other metal, while portions of the electric fluids 
set free at the metallic surfaces, flow in opposite 
directions through the connecting wire; that of the 
vitreous electricity being uniformly from the metal 
least acted on to the other. 

107. Simple voltaic circles maybe formed of vari- 
ous materials, for metallic substances are not essen- 
tial to the production of electrical currents. They 
can be produced by layers of charcoal and plumbago, 
of slices of muscle and brain, or of beet root and 
wood. Other liquids than water may also be used 
with metals, such as a fused metallic chloride, iodide, 
or fluoride. What is requisite, is, that the fluid 
should be decomposable by electricity, and that it 
should act with more energy on one of the metallic 
surfaces, than on the other. 

The simple voltaic circle in ordinary use is com- 
posed of a pair of zinc and copper plates excited by 
an acid solution. The form and size of the apparatus 
varies exceedingly; in one of the most advantage- 
ous, the copper is made into an oblong narrow cup 
for containing the liquid; and the zinc plate is fixed 
between its sides with interposed blocks of wood to 
prevent contact. A more convenient form is a cup, 
made of two cylinders of sheet copper of unequal 
size, placed one within the other, and soldered 
together at the bottom, so as to leave an intermediate 
space for containing the zinc cylinder, and the acid 
solution. Two small copper cups, attached by wires 
to the upper edge of the zinc and copper cylinders, 
are useful appendages; for by filling them with mer- 
cury, the voltaic circuit may be closed or broken 
with ease and expedition. 

Another kind of circle may be formed by coiling 
a sheet of zinc and copper round each other, so that 
each surface of the zinc may be opposed to one of 
copper, and be separated from it by a small interval; 
an apparatus of this kind has been made of plates 



68 ELEMENTS OF CHEMISTRY. 

60 feet in length. Dr. Hare contrived this arrange- 
ment and called his apparatus the calorimotor, on 
account of its great power in igniting metals. 

108. The intensity of the electricity, set in motion 
by a single pair of plates, is so feeble, that it requires 
the aid of a delicate apparatus to render it percepti- 
ble. 

By connecting a number of these simple circles 
together, the intensity of the electrical current may 
be increased at pleasure. 

By the term intensity ', is meant the energy or effort 
with which a current is impelled, and which is alto- 
gether independent of the quantity of the fluid set 
in motion. 

109. The Galvanic Battery. — The first combina- 
tion described by Volta, consisted of a vertical series 
of zinc and copper plates, each pair separated from 
those adjoining by pieces of cloth somewhat smaller 
than the plates : and moistened with a saturated solu- 
tion of salt. In these compound circles, it is essential 
that the same order of arrangement of the metals be 
preserved thoughout the whole, that is, if the zinc 
plate be the lower one of the upper pair, it must be 
the lower one of all the others. For, as the vitreous 
electricity always flows from the copper to the ad- 
joining zinc plate, and as the electrical energy, or 
intensity of the whole pile, is the sum of the energy 
or intensity of the several circles that compose it, it 
is evident that if the order be inverted in any num- 
ber of pairs, the direction of the current will also be 
inverted, and the effect of an equal number of pairs 
differently arranged will thereby be neutralized. 

The quantity of the electricity disengaged, depends 
upon the intensity of the chemical action, and it is 
found that this is a maximum at the moment when 
the fluid and plates come in contact. In order there- 
fore, to obtain this maximum in a compound circuit, it 
is requisite that the chemical action should take place 



daniell's constant battery. 69 

in all the pairs of plates at the same moment, which 
cannot be effected in the pile. 

110. The old arrangement of the pile has therefore 
been abandoned, and the best batteries are now con- 
structed on the plan of Dr. Hare, by soldering plates 
of zinc and copper together, and cementing them in 
a box, in grooves at the distance of a quarter of an 
inch apart. To the box containing the plates is 
attached lengthwise, another box of equal dimen- 
sions, for containing the acid solution when the bat- 
tery is not in use. The whole turns on an axle so 
as to admit of the fluid being poured into all the cells 
at the same instant by a quarter revolution of the 
axle. The trough turns on copper pivots that rest 
on copper bearings, and have a metallic communica- 
tion with the extreme plates, so that the electrical 
circuit can be completed by attaching wires to the 
fixed copper bearings. 

The acid solution is made by mixing 100 parts, by 
measure, of water with A\ of sulphuric acid and 4 of 
nitric acid. 

111. In all these arrangements, the maximum 
effect is produced at the moment of immersion, and 
the intensity of the chemical action continually de- 
creases. This is found to be owing to the decom- 
position of the sulphate of zinc, by the copper plate 
and the consequent precipitation upon the latter, of 
a film of metallic zinc, which operates by reducing 
the extent of the copper surface that is exposed to 
the chemical action. 

112. Daniell's constant Battery. — Professor Dan- 
iell has constructed a battery in which the surface of 
the copper is kept bright by a constant deposition of 
metallic copper on its surface, and in which the ac- 
tion is maintained for many days without the least 
diminution. Each cell of this battery is a cylindrical 
copper vessel of 3^ inches in diameter, within which 
is a cylindrical vessel of porous earthenware. A 



70 ELEMENTS OF CHEMISTRY. 

rod of amalgamated zinc occupies the centre and 
rests by across piece of wood upon the earthen cylin- 
der. The space within the latter is filled with 
water acidulated with one eighth part of its bulk 
of oil of vitriol, and the space without, with the same 
liquid saturated with sulphate of copper. A shelf is 
placed on the outside of the earthen cylinder, on 
which solid sulphate of copper is placed, so as to 
keep the solution constantly saturated. A battery 
thus constructed of twenty similar cells is capable of 
decomposing the alkalies, and of exhibiting the most 
interesting phenomena of voltaic electricity. 

113. Theory of Electro-chemical Action* — In 
these experiments the water between the metallic 
surfaces is decomposed, the oxygen appearing at the 
zinc, and the hydrogen at the copper surface. The 
former unites with the metal, the oxide which is thus 
formed is dissolved by the acid, and the metallic 
surface of the plate is in this way kept clean. 

Yet, although the oxygen is thus disengaged at 
one surface and the hydrogen at the other, it seems 
certain that there is no conveyance of either gas 
through the water. It is the oxygen of the aqueous 
particles in contact with the zinc, that accumulates 
on that surface, and the hydrogen of the particles in 
contact with the copper, that accumulates there. In 
order to explain these phenomena, we must suppose 
that the particles which compose the voltaic circuit 
assume opposite polarities. Thus we may conceive 
that the zinc plate attracts the negatively electrified 
oxygen of the particle of water next to it, setting the 
hydrogen free, which unites to the oxygen of the next 
particle, and so on ; at the same time the negatively 
electrified copper attracts the positive hydrogen of 
the particle of water in contact with it, and the oxy- 
gen with which it was united is set free, and unites 
with the atom of hydrogen of the adjoining particles, 
set free by the attraction of the zinc, for its oxygen. 
In this way there is a simultaneous and continuous 



ELECTRO-CHEMICAL ACTION. 71 

decomposition and recomposition of the particles of 
water in a line between the two plates. 

The negative electricity which was in combination 
with the oxygen is thus set free, and accumulated at 
the zinc plate, and the positive electricity which was 
in combination with the hydrogen is set free and ac- 
cumulated at the copper plate, and ^being attracted 
by each other, currents of vitreous and resinous elec- 
tricities are established along the connecting wires in 
opposite directions; namely, a current of the former, 
from the copper to the zinc, and of the latter, from 
the zinc to the copper. 

114. It is found that the quantity of electricity set 
in motion, is exactly in proportion to the energy of 
chemical action between the positive plate, and the 
solution in which the plates are immersed, and also 
that the peculiarities which distinguish this action 
from ordinary chemical action, namely, that it is 
altogether suspended in respect to one plate and 
greatly increased in respect to the other; cease, when 
the continuity of the circle is broken. 

115. When the extremities of the wires which 
complete the circuit in a voltaic battery, instead of 
being brought into contact, are immersed in a vessel 
of water, the electrical current decomposes the water. 
The vitreous current that passes from the copper 
plate, attracts the negative oxygen of the adjoining 
particle of water, and the resinous current from the 
zinc plate, attracts the positive hydrogen of the par- 
ticle of water next to it, and a series of decomposi- 
tions and recompositions of the particles, in a straight 
line between the wires, takes place simultaneously. 

The surfaces, whether metallic or non-metallic, at 
which the positive and negative electricities are disen- 
gaged in the voltaic circuit, are termed electrodes by 
Faraday, form q%sxf£ov 9 and o5oj, a way. He distin- 
guishes them into anode and cathode, the former being 
the electrode at which the positive electricity is sup- 



72 ELEMENTS OF CHEMISTRY, 

posed by him, to enter, and the latter, that by which it 
leaves the liquid. The anode may be more accu- 
rately stated to be the electrode, at which the nega- 
tive, and the cathode, that at which the positive elec- 
tricity accumulates, the former corresponding to the 
zinc, and the latter to the copper surface of the bat- 
tery. 

116. The current of electricity thus established 
along the connecting wires of a voltaic battery, not 
only produces chemical decomposition, but will ignite 
and melt metallic wires, charge a Leyden jar, and 
exhibit all the phenomena of ordinary electricity. 

117. Influence of the electric current on the mag- 
netic needle. — If a magnetic needle be placed along 
side of and parallel to the connecting wire of a voltaic 
circuit, the needle will deviate from its position, ac- 
cording to certain invariable laws. If the needle be 
suspended so as to vibrate in a horizontal plane, and 
be placed above the connecting wire, the pole which 
is next the positive electrode will be deflected to the 
right, which, where the line of direction of the wire 
and the magnet is north and south, will be to the 
westward. If it be placed under the wire, the same 
pole will be deflected to the left or to the east. If 
the needle be suspended so as to vibrate in a vertical 
plane, and be placed on the right or western side of 
the wire, the pole which is next to the positive elec- 
trode will be deflected towards the ground, and when 
placed on the left or eastern side, will be deflected 
upwards. 

118. The Galvanometer. — It is found that the 
angle of deflection bears a constant relation to the 
quantity of the electrical fluid which passes along 
the wire, and this property of electrical currents in 
deflecting a magnetic needle, furnishes a delicate me- 
thod of ascertaining their existence and quantity. 
An instrument called a galvanometer, has been con- 
structed for this purpose. It consists of several rec- 



THE THERMO-MULTIPLIER. 73 

tangular coils of wire, separated from each other by 
being wound round with silk, and communicating 
with the positive electrode by one end, and with the 
negative by the other. A delicately suspended mag- 
netic needle is placed in the plane of the rectangle, 
and as the current, in its progress along the wire, 
passes repeatedly above and below the needle in 
opposite directions, the whole tendency, both of the 
upper and lower current, is to deflect the needle in 
the same direction. The degree of deflection is 
measured on a graduated arc attached to the needle. 

119. Electricity from the unequal distribution of 
Heat. — The disturbance of the electrical equilibri- 
um, which is caused by friction and chemical action, 
is also caused by the unequal distribution of heat. 
A wire of uniform density and thickness shows no 
signs of electricity when one end of it is heated. But 
if there be any obstacle to the passage of the heat, 
a current of positive electricity will begin to flow from 
the heated part towards the point where the obsta- 
cle exists. So likewise if heat be applied to the point, 
at which two bars of different metals are soldered 
together, and their free extremites be connected by a 
wire, a feeble voltaic circle will be formed ; and if 
cold, instead of heat, be applied to the point of union, 
the direction of the electric current will be reversed. 
The metals which by their combination exhibit these 
phenomena, are bismuth, platinum, lead, tin, copper 
or silver, zinc, iron, and antimony ; the first and last 
named being the most powerful combination, and the 
current of positive electricity flowing through the 
wire from the first to the last mentioned metal. 

120. The Ther mo-multiplier. — Several pairs of 
bars of bismuth and antimony may be joined toge- 
ther, so as to form a compound circle, possessing a 
very feeble electricity, but strongly affecting a mag- 
netic needle. The thermo-electric pile, as it is term- 
ed, is the most delicate and accurate measure of the 

7 



74 ELEMENTS OP CHEMISTRY. 

changes of temperature that has yet been discovered. 
Melloni used an instrument of this kind in his admi- 
rable researches into Radiant Heat. Thirty pairs of 
slender bars or needles of bismuth and antimony, 
being soldered together, two by two, at their alternate 
ends, and packed into a cylindrical case, were con- 
nected by their extreme ends with a very delicate 
galvanometer. These bars were so slender, that the 
circular area of the containing case was not larger 
than the bulb of an ordinary thermometer; and so 
delicate was the instrument, that the heat of the 
hand at the distance of thirty feet, sensibly affected 
the needle of the galvanometer. 



THE 

PRINCIPLES OF CHEMISTRY. 

PART FIRST- 
inorganic CHEMISTRY. 

CHAPTER I. 

THE PONDERABLE ELEMENTS. 

121. The infinite variety of ponderable substances 
by which we are surrounded, results from the vari- 
ous combinations of a few elements. Those sub- 
stances which have hitherto resisted all our efforts 
to decompose them, are regarded as simple elemen- 
tary bodies. The number of these bodies at present 
known is fifty-five, and they may be divided into 
two great classes, metallic and non-metallic. Those 
belonging to the former class are distinguished by 
being conductors of electricity, by their opacity, and 
by a peculiar lustre which is termed the metallic lus- 
tre. Bodies of the latter class are distinguished by 
being non-conductors of electricity, by being more or 
less transparent, and by the absence of the metallic 
lustre. It will be most convenient to describe the 
latter class in the first place. 



76 PRINCIPLES OF CHEMISTRY. 

Section I. 
The Non-metallic Elements. 

122. These are thirteen in number, viz: 
Oxygen, Carbon, 
Chlorine, Boron, 
Iodine, Silicon, 
Bromine, Sulphur, 
Fluorine, Phosphorus, 
Nitrogen, Selenium. 
Hydrogen, 

123. Oxygen. — Oxygen is one of the most abun- 
dant substances in nature. It forms about a fifth 
part of the atmosphere, more than a third part of the 
solid crust, and eight-ninths of the waters of the globe. 
It enters into the composition of nitre, (nitrate of po- 
tassa,) red lead, (red oxide of lead,) black oxide of 
manganese, chlorate of potassa, and most acid and 
saline compounds. It was thought at one time to 
be the sole acidifying principle, and was therefore 
named oxygen, from o|u$, acid, and yswsw, to gene- 
rate. 

Oxygen gas was discovered by Priestley in 1774, 
and called by him dephlogisticated air. Scheele, 
without any knowledge of Priestley's discovery, 
obtained it a year or two afterwards, and called it 
empyreal air; it was also termed vital air by Con- 
dorcet. 

124. Oxygen gas may be obtained by heating, to 
a red heat, the pulverised black oxide of manganese 
in an iron flask, to which a bent tube is attached, 
and collecting the gas in the inverted jar of a pneu- 
matic trough. The oxide consists of manganese 27.7, 
and oxygen 16, and parts with one fourth part of the 



OXYGEN. 77 

latter. Every 43.7 grains of pure oxide yield four 
grains or 12 cubic inches of oxygen gas. 

Oxygen gas may be obtained sufficiently pure for 
ordinary purposes, by heating nitre (nitrate of potas- 
sa) to a red heat in an iron flask. The salt is decom- 
posed, and every 102 grains will yield about sixteen 
grains or 36 cubic inches of gas. It is, however, less 
pure than that obtained by the former, or the follow- 
ing process. 

Oxygen is obtained in the purest state and great- 
est quantity, in decomposing by heat the chlorate of 
potassa in a retort, the glass of which contains no 
lead. This salt contains, in every 122§ grains, 48 
grains of oxygen, which are separated by heat, so 
that an ounce troy of the salt yields 187 grains, or 
543 cubic inches of gas. 

125. Oxygen gas is destitute of taste or smell. Its 
specific gravity is to that of atmospheric air as 1.1026 
to 1; 100 cubic inches of oxygen gas, when the tem- 
perature is at 60° F. (15.5° C.) and the barometer at 
30 inches, weigh 34.2 grains. 

Oxygen gas refracts light less than any other 
known substance. It is a non-conductor of electri- 
city, and is the most perfect negative electric known. 
It has never been obtained uncombined in any other 
form than that of a permanently elastic fluid or gas. 

Water dissolves oxygen gas very sparingly, 100 
cubic inches absorbing but about three or four cubic 
inches of the gas. 

126. One of the most remarkable properties of 
oxygen gas is its power of supporting combustion. 
If a taper or piece of wood, on which the slightest 
spark is visible, be plunged into a vessel of oxygen 
gas, it is immediately rekindled and burns with great 
brilliancy. Phosphorus burns in it with so vivid 
a light as to be painful to the eye. Charcoal burns 
with beautiful scintillations, and the combustion of 



78 PRINCIPLES OP CHEMISTRY. 

iron or steel wire exhibits still more dazzling corus- 
cations. All substances that are capable of burning 
in the open air, burn in oxygen gas with still greater 
brilliancy. It is found that the gas is itself consumed 
in this process, which is merely a rapid combination 
of oxygen with the burning body, accompanied by 
the extrication of light and heat. 

127. Oxygen gas is necessary to the support of 
animal life, for no animal can live in an atmosphere 
which does not contain uncombined oxygen gas. Air, 
from which the oxygen has been abstracted by a 
burning body, or by chemical affinity, is instantly 
fatal to an animal. An animal cannot live long in 
pure oxygen gas, for the system becomes highly ex- 
cited, debility ensues, and the animal dies from over 
excitement. 

Oxygen combines with all the other elementary 
bodies, forming compounds that are termed oxides 
or acids. 

128. Chlorine. — Chlorine is one of the component 
parts of common salt, which is extensively diffused 
in nature as a rocky mineral, and which also forms 
about three parts in a hundred of the waters of the 
ocean. 

Chlorine was discovered by Scheele in 1774, and 
called by him dephlogisticated marine acid. It 
was called oxygenated muriatic or oxy-muriatic acid, 
by the French chemists, who erroneously supposed 
it to be an acid. 

129. Chlorine is obtained from common salt by 
mixing three parts thereof, with one part of black 
oxide of manganese, two parts of sulphuric acid, and 
two parts of water. The mixture is gently heated 
in a glass retort, and the chlorine collected in a ves- 
sel over hot water. 

130. Chlorine is a permanently elastic fluid of a 
yellowish green colour, and derives its name from 



CHLORINE. 79 

2*tt£os, green. Its taste is astringent, and its odour 
very disagreeable and suffocating. It is one of the 
most fatal to animal life of all the gases. Its specific 
gravity is 2.47, and 100 cubic inches of the gas at 
60° F. and 30 in: Bar. weigh 76.59SS grains. Under 
the pressure of four atmospheres, chlorine becomes a 
liquid of a bright yellow colour, which remains fluid 
at very low temperatures. 

Both in the gaseous and liquid state, it is a non- 
conductor of electricity and a negative electric. Hot 
water does not absorb this gas, but cold water ab- 
sorbs twice its volume at the common pressure, and 
yields it again when heated. When moist chlorine 
gas is exposed to a temperature of 32° F. (0° C), 
yellow crystals are formed, which are a combination 
of chlorine and water. 

131. The most powerful means of chemical de- 
composition which we possess have hitherto failed 
to produce any change in chlorine, and it is therefore 
to be regarded as a simple elementary substance. 

Chlorine resembles oxygen, in being in some re- 
spects a supporter of combustion. A lighted taper 
burns in it for a short time with a small red flame, 
and emits a large portion of smoke. Tin, copper, 
arsenic, antimony, zinc, when in a state of powder, 
or fine leaves, and phosphorus, take fire spontane- 
ously in chlorine gas, and combine with it. 

Chlorine combines with nearly all the other ele- 
mentary bodies, forming compounds that are called 
chlorides. 

132. A very remarkable property of this element 
is its power of destroying animal and vegetable 
colours, and the volatile odoriferous principles of 
putrefying organic matter, and contagious effluvia. 
Colours that have once been removed by it cannot 
be restored. Its property of destroying contagious 
effluvia, has been extensively and successfully ap- 



80 PRINCIPLES OP CHEMISTRY. 

plied to the fumigation of hospitals in cases of con- 
tagious disease. 

Chlorine may be known by its peculiar colour 
and suffocating smell. When the hand is plunged 
into a vessel of this gas, a very perceptible degree of 
warmth is felt. 

The presence of chlorine in any compound may 
be detected by a solution of the nitrate of silver, a 
salt hereafter to be described. It occasions, in the 
compounds of chlorine, a white precipitate, which 
becomes black by exposure to light. 

133. Iodine. — Iodine exists in sea water and in the 
water of certain saline springs, and enters into the 
composition of many marine plants and zoophytes. 
It was discovered in the year 1812, by Courtois, a 
manufacturer of nitre at Paris, 

Iodine is prepared from the impure alkaline salt 
formed by burning sea weeds. This alkali is refined 
for the use of the manufacturers of soap, and the 
liquors which remain after the crystallization of the 
salt, contain it in considerable quantities. 

134. Iodine is a soft, friable, opaque solid, closely 
resembling micaceous iron ore in colour and lustre, 
and like that mineral it is usually in crystalline scales. 
It crystallizes in large rhomboidal plates, the primi- 
tive form of which is a rhombic octohedron. 

The specific gravity of iodine is 3.08. It fuses at 
225° F. (107° C), and boils at 347° F. (175° C), and 
when it is moistened with water it sublimes at low 
temperatures. Its vapour is of a rich indigo or 
violet colour, and hence it derives its name from the 
Greek word *ofy$, violet coloured. The density of 
this vapour is 8.716, according to Dumas, and 100 
cubic inches weigh 269.S638 grains. 

Iodine is a non-conductor of electricity, and a 
negative electric. Its taste is acrid, and its odour 
strongly resembles that of diluted chlorine. Water 
dissolves about one seven thousandth part of its 



BROMINE. 8 1 

weight of iodine, and the solution has a yellowish 
brown colour. It is readily soluble in alcohol and 
ether, communicating to those liquids a deep reddish- 
brown colour. 

Iodine combines with most of the elemental bodies, 
and its compounds with them are called iodides. 

Its action upon vegetable and animal colours, re- 
sembles that of chlorine, although it is more feeble. 

The presence of iodine may be known by the 
violet hue of its vapour. A more delicate test is 
starch, with which it forms a compound of a deep 
blue colour; and so delicate is this test, that it will 
communicate a perceptible blue tint to a liquid con- 
taining one part in 450,000 of iodine. 

135. Bromine. — Bromine was discovered in 1826, 
by Balard of Montpelier. It exists in nature asso- 
ciated with iodine, and is obtained from the same 
substances as that element, which it closely resem- 
bles in its properties. 

It derives its name from the Greek word j3£«j*o$, 
signifying a strong offensive odour. 

136. Bromine, at the ordinary temperature, is a 
liquid of a garnet colour, so deep as to be almost 
opaque. Its odour resembles that of chlorine, being 
highly disagreeable and suffocating. Its specific 
gravity is 3. At the ordinary temperature it emits 
deep red-coloured vapours; at 116.5° it boils, and 
between 0° and — 4° it becomes a brittle solid. Bro- 
mine is a non-conductor of electricity. It is a nega- 
tive electric, and has resisted all attempts to decom- 
pose it. It is soluble in water, alcohol, and ether, 
and when exposed to a temperature of 32°, in con- 
tact with water, forms a hydrate that crystalizes in 
beautiful red octohedral crystals. 

The vapour of bromine extinguishes a lighted ta- 
per, the flame of which becomes green at the base 
and red in the upper part, before going out. 

Some inflammable substances take fire by contact 



82 



PRINCIPLES OF CHEMISTRY. 



with bromine. It acts with energy on organic sub- 
stances, stains the skin yellow, and bleaches solutions 
of litmus and indigo. 

The presence of bromine may generally be ascer- 
tained by means of chlorine, which disengages it 
from most of its combinations. 

Bromine combines with nearly all the elemental 
bodies, and its compounds are called bromides. 

137. Fluorine. — This element is so called from 
the mineral termed Fluor Spar, of which it is a com- 
ponent part. Although fluorine has been isolated, 
yet the difficulty of procuring vessels on which it does 
not act, has prevented its accurate examination. 
At the ordinary temperature it is a gas of a yellowish 
brown colour, which has an odour resembling chlo- 
rine and burnt sugar, and which bleaches vegetable 
colours. It is the only simple element which has 
not been made to combine with oxygen. 

138. Nitrogen. — Nitrogen enters into the compo- 
sition of atmospheric air, forming about four fifths 
of the atmosphere. Its peculiar properties were 
first noticed by Dr. Rutherford of Edinburgh, in 
1772. Lavoisier in 1775, ascertained it to be a con- 
stituent part of the atmosphere, and called it azote, 
from a, and J«^ life. Its present name was applied to 
it on account of its being the base of nitric acid. 

Nitrogen is most conveniently prepared by burn- 
ing phosphorus in a small floating cup, under a bell 
glass in a pneumatic trough. The sole product of 
combustion is phosphoric acid, which is speedily 
absorbed by the water, leaving only nitrogen in the 
receiver. If the vessel be graduated, it will be seen 
that the portion consumed, which is oxygen gas, 
amounts to one fifth of the whole quantity. 

Nitrogen gas is colourless, and devoid of smell and 
taste. It does not change the blue colour of vege- 
tables, and is characterized by negative, rather than 
by positive qualities. It is not a supporter of com- 






HYDROGEN. 83 

bustion, but extinguishes all burning bodies that are 
immersed in it. It is not inflammable. It is not a 
supporter of animal life, although it has no delete- 
rious properties, but causes death by the privation 
of oxygen. 

One hundred cubic inches of water absorb one 
and a half cubic inches of this gas. Its specific gra- 
vity is .9727, and 100 cubic inches weigh 30.165 
grains. Nitrogen refracts light feebly. It has never 
been decomposed, nor has it been compressed into a 
fluid. It is an electro-positive element, appearing 
at the negative electrode, when compounds that 
contain it are decomposed by electricity. 

139. Hydrogen. — Hydrogen, so termed from *$»£, 
water, and yswetv, to generate, is one of the elements 
of water. Its properties were discovered by Caven- 
dish, in the year 1766, and it was named by him in- 
flammable air. It was also called phlogiston, from 
the supposition that it was the matter of heat. 

Hydrogen exists naturally as a gas, and has never 
been liquefied. It may be obtained by passing the 
vapour of water through a tube filled with iron wire, 
kept at a red heat. The oxygen unites with the 
iron, and the hydrogen which is set free, may be col- 
lected in convenient vessels by dipping the end of 
the tube in the water of a pneumatic trough. A 
more convenient method of obtaining it, consists in 
submitting fragments of iron or zinc to the action of 
dilute sulphuric acid, consisting of one part of acid 
to four or five of water. The oxygen of the water 
unites with the metal, and the hydrogen is set free. 

140. Pure hydrogen gas has neither smell, taste, 
nor colour. As commonly prepared, it has a faint, 
disagreeable smell, owing to the impurity of the ma- 
terials from which it is prepared. 

141. It refracts light more powerfully than any 
other gas, having 6.6 times as great a refractive 
power as atmospheric air. Its specific heat is also 



PRINCIPLES OP CHEMISTRY. 

greater than that of any other body, being to that 
of air as 13.08 to 1, and to that of water as 3.88 to 
1. It is the lightest of all known ponderable bodies, 
being 300,000 times lighter than platinum; and its 
specific gravity being .0689, or precisely 16 times 
lighter than oxygen gas, so that 100 cubic inches 
weigh 2.1367 grains. 

Hydrogen gas is highly inflammable, and burns 
with a yellowish blue flame, and feeble light. When 
mixed with 2§ times its bulk of atmospheric air, it 
detonates violently by the electric spark, or the ap- 
proach of flame. The explosion is far more violent 
when the hydrogen is mixed with half its bulk of 
pure oxygen gas. 

Hydrogen gas extinguishes the flame of a lighted 
taper immersed in it, and destroys animal life. It is 
not however immediately deleterious, as the lungs 
may be inflated with it a few times in succession, 
without injury. 

142. When a stream of hydrogen, or other deto- 
nating gas issues from a small aperture, it speedily 
blends with the atmospheric air, and, if set on fire, 
burns in a series of continued but feeble explosions. 
These may be rendered audible by burning the jet 
in a tube of glass, or other material; which gives 
musical sounds of great variety of intonation, ac- 
cording to the size of the flame or the tube. 

One hundred cubic inches of water absorb lj cubic 
inches of hydrogen gas. 

143. A large quantity of heat is evolved in the com- 
bustion of hydrogen gas, the quantity of ice melted 
by burning a pound, being estimated by Lavoisier 
at 295.6, by Dalton at 320, and by Dr. Crawford at 
480 pounds. The most intense heat that has yet 
been procured, is caused by burning hydrogen in 
oxygen gas. In Dr. Hare's blowpipe the gases are 
collected in separate vessels, and conducted from 
them through tubes terminating in a common aper- 



CARBON. 



85 



tare, at which the jet of the mixed gases is inflamed. 
In Newman's blowpipe, as now modified, the gases 
are condensed by a syringe into a strong metallic 
box, and burned at the extremity of a tube, the in- 
terior of which is filled with closely packed layers 
of wire gauze, that effectually prevent the flame 
from communicating to the explosive mixture in the 
box. 

Hydrogen unites with the other simple elements, 
giving rise to a great number of compounds. It is 
the electro-positive element in most of those combi- 
nations. Its compounds are called hydrogurets. 

144. Carbon. — Carbon is one of the most exten- 
sively diffused elements in nature. It is found in 
crystals, which are termed diamonds; graphite, or 
black lead is almost pure carbon ; and it is obtained 
nearly pure, in the form of charcoal, by burning 
wood in close vessels, so as to expel all the volatile 
portions. Neither acids nor alkalies have any action 
on it. 

145. Diamond, or crystallized carbon, is one of 
the rarest and most highly prized substances in na- 
ture. It occurs in perfect crystals, and in roundish 
grains of crystalline structure. Its primitive form 
is the octohedron, and its secondary crystals are 
usually curvilinear polyhedrons. Its structure is la- 
mellar, with joints parallel to the faces of the primi- 
tive crystal. 

It is satisfactorily shown from the optical proper- 
ties of the diamond, that it must originally have 
been soft, and that it was formed by a slow concre- 
tion. Dumas found the diamond when burnt, to 
to leave behind a slender skeleton of inorganic matter. 
It is in general colourless, but sometimes with a 
tinge of gray, blue, red, yellow, green, brown, or 
black; its lustre is highly splendid, and it refracts 
light powerfully; its sp. gr. is 3.52, and it is the 
hardest substance in nature. It is infusible, and un- 

8 



86 PRINCIPLES OF CHEMISTRY. 

dergoes no change by exposure to the most intense 
heat in a close vessel, but slowly consumes away 
when heated to a white heat in the open air, and 
burns with great brilliancy in melted nitre. 

146. Anthracite coal and graphite are included 
in the same mineral species, and consist of carbon in 
a state of great purity. Graphite differs from an- 
thracite in being soft and unctuous to the touch, and 
in leaving a grey streak on paper. It is this proper- 
ty which renders it so useful a material for drawing 
pencils. Graphite may be formed artificially, by 
exposing charcoal to the action of melted iron. Its 
sp. gr. is 2.5, and it conducts heat and electricity. 
Graphite crystallizes in rhombohedrons, so that car- 
bon is a di-morphous element. It is perfectly opaque, 
and is often found in brilliant lamellar hexagonal 
tables. 

147. Charcoal is black, porous, hard, and brittle; 
it conducts heat very slowly, and is a good conduc- 
tor of electricity. It is insoluble in water, and has 
scarcely any action upon acids or alkalies. It is in- 
fusible, and undergoes no other change by exposure 
in a close vessel to the most intense heat, than be- 
coming so firm and hard as to scratch glass. 

14S. Recently prepared charcoal, dry and yet 
warm, gradually absorbs large quantities of several 
kinds of air, the greater part of which is expelled 
when it is again heated to a red heat. The quantity 
thus absorbed is, in the case of some of the readily 
liquefied gases, 90 times its own volume. It absorbs 
1.75 times its bulk of nitrogen, 7.5 of hydrogen, and 
9.25 of oxygen. 

From this cause, fresh burned charcoal increases 
from 9 to 18 per cent, in weight, by exposure to a 
damp atmosphere. Charcoal also absorbs the odo- 
riferous and colouring matters of most animal and 
vegetable substances. Whenmeat which has been 
tainted, is carefully washed in cold water, and then 



SILICON. 87 

boiled in water in which pieces of red hot char- 
coal have been plunged, it is entirely sweetened. 
When coloured or odoriferous liquids are filtered 
through freshly burned charcoal, they are deprived 
of the greater part of their colour and smell. The 
most efficacious charcoal for this purpose is prepared 
from animal matters, and it loses its property after 
being used, but has it restored by heating anew to 
redness with a fresh portion of animal matter. 

When strongly heated in the open air, charcoal 
burns slowly without smoke or residue. In oxygen 
gas it burns rapidly, and with brilliant scintillations. 
The compounds of carbon are called carburets. 
4 149. Boron. — A salt, known by the name of borax, 
has long been obtained from India as an article of 
commerce, being highly valued as a flux by the 
workers in metals. This salt is a compound of the 
alkaline base, soda, and a peculiar acid, which has 
received the name of boracic acid. 

Boracic acid itself was ascertained by Davy, in 
1807, to be a compound of oxygen, with a peculiar 
and hitherto undecomposed base, that is termed 
Boron. 

Boron is obtained in the form of a dark olive co- 
loured powder, tasteless, inodorous, insoluble, and 
infusible. It bears the most intense heat in close 
vessels, without change, and when heated in the 
open air to 600°, it suddenly takes fire and burns, 
being converted into boracic acid. Its specific grav- 
ity is about 2. and it is a non-conductor of electri- 
city. 

Boron is obtained by heating potassium with bo- 
racic acid, in a copper tube. They combine with 
the extricatipn of much light and heat, and the bo- 
ron is freed from impurities by washing with warm 
water. 

150. Silicon. — One of the most extensively dif- 
fused substances in the mineral kingdom, is the earth 



88 PRINCIPLES OF CHEMISTRY. 

called silex, in its various modifications of quartz, 
rock crystal, and sand. Sir Humphrey Davy brought 
pure silex into contact with the vapour of potassium, 
and found that it was decomposed, and the potas- 
sium converted into an oxide by the oxygen which 
it had abstracted from the silex. He thus ascertained 
silex to be a combination of oxygen, with a peculiar 
undecompounded substance, which is separated in 
the above experiment, and to which the term silicon 
has been given. 

151. Silicon is an infusible solid, of a dark nut- 
brown colour. It is a non-conductor of electricity. 
When first prepared it is soluble in a solution of 
chlorohydric acid, and of caustic potassa; although 
the sulphuric and nitric acids, even at a boiling 
heat, have no action on it. It ^ burns readily and 
vividly in the open air, and becomes coated with 
silex. If this coating be removed, the silicon be- 
neath is found to have been condensed and altered 
by the heat, to which it has been exposed. It is 
now perfectly incombustible, and no longer soluble 
in chlorohydric acid, or caustic potassa. 

Silicon burns vividly when brought into contact 
with carbonate of potassa, or soda, at a temperature 
below that of redness. 

152. Sulphur. — Sulphur is found in a state of pu- 
rity in volcanic countries, and also exists in large 
quantities in combination with iron, and other me- 
tals. It is obtained for commercial purposes by dis- 
tillation from these combinations. 

Sulphur also exists in organic bodies, being found 
in the yolk of eggs, and in black mustard seed. 

153. Sulphur, like carbon, is a dimorphous body. 
It is found native, and it crystallizes front its vapour, 
and from certain solutions, in the form of the right 
rhombic octohedron. On the other hand, the crys- 
tals obtained by slowly cooling a mass of melted 
sulphur, till a crust is formed, and then pouring the 



SULPHUR. 89 

interior liquid from the surrounding solid mass, are 
transparent, oblique, rhombic prisms; after a few 
days, these crystals undergo a molecular change, be- 
come opaque, and full of fissures in the plane of the 
right rhombic octohedron, which is the form of the 
native crystal. 

154. Sulphur is a brittle solid, of a light yellow 
colour. It is insoluble in water and alcohol, is taste- 
less, emits a peculiar odour, and becomes negatively 
electrified when rubbed, and is a non-conductor of 
electricity. Its specific gravity is 1.99. It is vola- 
tile and fusible, begins to evaporate at 170°, and to 
fuse at 205°. At 220° it is completely fluid, but 
when heated to 350°,it becomes a soft tenacious solid, 
and acquires a reddish-brown tint. If sulphur in 
this state be plunged in cold water, it forms a plastic 
transparent mass, which slowly regains the hardness 
of common sulphur, and is much used for taking fine 
impressions of coins and medals. At 482° it again 
becomes liquid and boils at 600°. It is now rapidly 
volatilised, and condenses in detached crystalline 
grains, which form what is termed the flower of sul- 
phur. 

The vapour of sulphur has a deep yellow colour, 
and the specific gravity of 6.648. 

When sulphur is heated in the open air, it kindles 
spontaneously. It burns slowly with a faint blue 
light at 180° or 190°, and with so small an evolution 
of heat as not to inflame gunpowder. At 300° its 
combustion is more rapid, and in oxygen gas it burns 
vividly with a bluish white flame. 

155. The vapour of sulphur is a supporter of com- 
bustion. If a piece of sulphur be dropped into a 
gun-barrel heated at the butt end to a red heat, and 
the sulphurous vapour which is formed be forced in 
a stream from the touch hole, iron wire will take 
fire in it and burn as brilliantly as in oxygen gas. 



90 PRINCIPLES OF CHEMISTRY. 

Sulphur combines with the other elementary bodies 
and its compounds are called sulphurets. 

156. Phosphorus — Phosphorus was discovered in 
1669, by Brandt, an alchemist of Hamburg. 

It is prepared from the ashes of burnt bones, which 
consist of lime combined with phosphorus and oxy- 
gen, forming phosphoric acid. They are mixed with 
water, and digested with half their weight of sul- 
phuric acid, which partially decomposes the phos- 
phate of lime. The clear liquid is separated by filtra- 
tion, evaporated to the consistence of syrup, mixed 
with one fourth its weight of charcoal powder, and 
strongly heated in an earthen retort, the beak of 
which is plunged in water. The charcoal decom- 
poses the phosphoric acid, and the phosphorus distils 
over in drops, and is collected under the water. 

157. Pure phosphorus is transparent and almost 
colourless. It has the consistence and lustre of wax. 
It fuses at 108°, and boils at 550°. Its specific gravity 
is 1.778, and it crystalizes in octohedrons. When 
melted phosphorus is cooled by being suddenly plung- 
ed in cold water, it becomes black and opaque, but 
recovers its original aspect, by fusion and slow cooling. 

Phosphorus is exceedingly inflammable ; it burns 
in common air with a bright white light, and its com- 
bustion in oxygen gas is brilliant in the highest de- 
gree. It undergoes slow combustion at common 
temperatures in atmospheric air, emitting a white 
vapour, an alliacious odour, and a faint light which is 
visible in the dark. It must therefore be preserved 
under water. The presence of very small quantities 
of the vapour of ether, or oil of turpentine, or of 
defiant gas, prevents the slow combustion of phos- 
phorus at low temperatures. 

Phosphorus takes fire spontaneously by pressure, 
friction, and percussion. It is soluble, by the aid of 
heat, in the essential oils. Its compounds are termed 
phosphurets. 



THE METALS. 91 

158. Selenium. — Selenium was discovered by 
Berzelius, and so called from cr^^, the moon, be- 
cause of its resemblance to the metal tellurium, in 
combination with which it exists, and for which he 
at first mistook it. It is found in minute quantities, 
combined with sulphur, and some of the metals. 

At the ordinary temperature it is a brittle solid, 
which is opaque, and of a dark leaden grey colour, 
and metallic lustre, when in masses of some thick- 
ness, but translucent and of a rich garnet colour, 
when in thin films, and of a deep brick red when 
reduced to powder. 

Its specific gravity is 4.3. It melts at a tempera- 
ture somewhat above that of boiling water, and sof- 
tens at 212°, and may then be drawn out into fine 
transparent threads of a red colour. At 650° it boils, 
and is converted into an inodorous vapour of a deep 
yellow colour. It is sublimed in close vessels, and 
condensed again without change. It conducts heat 
and electricity imperfectly, is insoluble in water, and 
unchanged by exposure to the air. 

It combines readily with oxygen when heated, 
and tinges the flame of the blowpipe of a light blue 
colour, exhaling so strong a smell of decaying horse- 
radish that -L-th of a grain will fill a large apartment 
with the odour. 



Section II. 

The Metals. 

159. The metals constitute a more natural assem- 
blage than the non metallic elements, and yet when 
we attempt to define them, there are but two quali- 
ties in which they all agree, namely, the peculiar 
lustre called metallic, and the power of conducting 
heat and eletricity. Even in these there is a wide 
difference between the extremes, and thej passage 



92 PRINCIPLES OF CHEMISTRY. 

from the non metallic to the metallic elements is 
gradual and not sudden. Thus sulphur and selenium 
are more closely allied to arsenic and tellurium, than 
either of them to many of the elements under their 
own class. 

160. Until the discovery of the metallic bases of 
the alkalies, which are lighter than water, the metals 
as a class were distinguished by their great weight; 
the specific gravity of iridium, the heaviest body 
known being 21.8, and that of chrome 5. 

161. Malleability and Ductility. — Some of the 
metals admit of being beaten into thin plates or 
leaves. The malleable metals are, gold, silver, cop- 
per, tin, platinum, palladium, cadmium, lead, zinc, 
iron, nickel, potassium, sodium, and solid mercury. 
The remaining metals are brittle, and some of them 
so much so as readily to be reduced to powder. 

Most of the malleable metals admit of being drawn 
out into wire, although the same metal does not 
always possess both qualities in the same degree. 
Gold, silver, platinum, iron, and copper, are the most 
ductile metals. 

162. Tenacity. — The tenacity of the metals varies 
greatly, as will be seen by the following table, stat- 
ing the number of avoirdupois pounds sustained by 
a wire .787 lines in diameter, 

Iron wire .... lbs. 549.25 

Copper 302.778 

Platinum .... 274.32 

Silver 187.137 

Gold .... 150.753 

Zinc 109.54 

Tin . . . . . 34.63 

Lead 27.621 

The tenacity of metals is greatly lessened by the 
process of annealing, which is that of very slow cool- 
ing. 

163. Metals differ greatly in hardness and elas- 
ticity, Titanium, manganese, and iron, will scratch 



FUSIBILITY. 93 

glass, while lead, potassium, and sodium, may be 
scratched by the finger nail. Iron and copper are 
the most elastic metals, and their sonorousness de- 
pends upon this quality. 

164. Crystallization. — Many of the metals have 
a distinct crystalline structure. Iron is fibrous; zinc, 
bismuth, and antimony are lamellated. Many of 
them may be obtained in distinct crystals, by slow 
cooling from their liquid state, and pouring out the 
melted metal from the surrounding solid mass. The 
resulting crystal is almost always the cube or regular 
octohedron. 

165. Fusibility. — Mercury is naturally liquid. 
Potassium and sodium fuse below the boiling point 
of water. Cadmium, tin, bismuth, lead, tellurium, 
arsenic, zinc, and antimony, fuse below a red heat. 
Silver, copper, and gold, fuse at a full red heat. Co- 
balt, nickel, iron, manganese and palladium require 
the highest heat of a smith's forge to fuse them ; and 
the remaining metals can only be perfectly fused by 
the oxyhydrogen blowpipe, or in the galvanic cir- 
cuit. 

Cadmium, mercury, arsenic, tellurium, potassium, 
sodium and zinc, are volatile. 

166. The metals are forty-two in number and may 
be conveniently arranged as follows: 

First Group. 

Metals forming acids with oxygen. 

Tellurium, Manganesium, 

Arsenicum, Titanium, 
Antimony — Stibium, Columbium, 

Chromium, Uranium, 

Vanadium. Osmium, 

Molybdenum, Tin— Stannum, 

Tungsten, Gold — Aurum. 



94 



PRINCIPLES OF CHEMISTRY. 



Second Group. 
Metals forming neither acids nor alkalies, but heavy, 

earthy, and mostly coloured oxides. 
Platinum, Lead — Plumbum, 

Palladium, Zincum, 

Rhodium, Cadmium, 

Iridium, Copper — Cuprum, 

Nickel um, Iron — Ferrum, 

Silver — Argentum, Cobaltum, 

Mercury — Hydrargyrum, Cerium, 
Bismuthum, Lanthanium. 

Third Group. 
Metallic bases of the Earths. 
Aluminium, Thorium, 

Yttrium, Zirconium. 

Glucinium, 

Fourth Group. 
Metallic bases of the Alkaline Earths. 
Magnesium, Strontium, 

Calcium, Barium. 

Fifth Group. 
Metallic bases of the Alkalies. 
Lithium, Sodium — (Natrium,) 

Potassium — (Kalium.) 

167. Tellurium.^-TeWmium was discovered in 
1798, by Klaproth. It is a rare metal, found only in 
small quantities in the gold mines of Transylvania. 

Its colour is intermediate between that of tin and 
lead. It has a bright metallic lustre, and lamellated 
structure. It is very brittle; its specific gravity is 
6.115; it fuses at a heat below redness, and is vola- 
tile at a red heat. Before the blow-pipe it burns 
rapidly with a blue flame, bordered with green, and 
is dissipated in gray-coloured pungent fumes. 

168. Arsenicum. — Arsenic is sometimes found na- 



CHROMIUM. 95 

tive, but more frequently in combination with sul- 
phur, iron, cobalt, and other metals. 

It is exceedingly brittle, has a bright metallic lus- 
tre, a crystalline structure, and a steel-gray colour. 
At 356° it sublimes slowly without liquefying, and 
in condensing crystallizes in rhombohedrons. Its 
fusing point has not been ascertained. Its specific 
gravity is 5.88. Its vapour has a strong odour of 
garlic. It tarnishes by exposure to the air, and when 
heated in contact with oxygen, is rapidly converted 
into a white oxide. 

169. Jlntimonium. — Antimony was discovered 
in the 15th century, by Basil Valentine. It is some- 
times found native, but its principal ore is the sul- 
phuret, from which it may be obtained, by heating 
the powdered ore, with half its weight of iron filings, 
in a covered crucible. Antimony is a brittle metal, 
of a light bluish gray-colour, having a lamellated 
structure. It possesses considerable metallic lustre, 
which tarnishes by exposure to the air. Its specific 
gravity is 6.7. It fuses at 810°, and may, by very 
slow cooling, be obtained in crystals, the primitive 
form of which is a rhombohedron. 

When heated to a white heat in a covered cruci- 
ble, and then suddenly exposed to the air, it takes 
fire and burns with a white light, and with the for- 
mation of white vapours that condense into small 
acicular crystals having a silvery lustre. 

170. Chromium. — Chrome was discovered in 
1797, by Vauquelin. The principal ore of chrome 
is its combination with iron. It is also found united 
with lead. 

Chromium is a brittle metal, almost infusible, of a 
yellowish white colour, and a distinct metallic lustre. 
It is scarcely acted on by the most powerful acids. 
Its specific gravity is 5. It is also obtained in the 
form of a black powder, which acquires a metallic 
lustre by pressure, and takes fire when heated in the 
open air. 



96 



PRINCIPLES OF CHEMISTRY. 



171. Vanadium. — Vanadium was discovered in 
1830, by Sefstrom in Swedish iron, although' its ex- 
istence as a distinct metal had been announced in 
1801, by Del Rio, of Mexico. Vanadium is found 
combined with iron and with lead. It has generally 
been obtained from its ore in the form of a heavy 
black powder, which assumes, under a strong pres- 
sure, a lustre like that of graphite, and which takes 
fire at a red heat. It may also be obtained in a 
crystalline mass, having a brilliant metallic lustre, 
and a white colour, and which is so brittle, that it 
falls to powder upon being moved. It is not oxi- 
dised by air or water at common temperatures. 

172. Molybdenum. — Molybdenum was announced 
as a distinct metal in 1778, by Scheele^ who did not, 
however, succeed in separating it from its ore. It is 
usually found combined with sulphur, or with lead. 

It is a brittle, grayish white, and almost infusible 
metal. Its specific gravity is 8.6. When heated in 
open vessels, it combines with oxygen and forms an 
acid. 

173. Tungstenum. — Tungsten is so called from 
the Swedish words, tung sten, heavy stone, on ac- 
count of the density of its ores. 

It is a metal of a grayish white colour, having a 
brilliant lustre. It is nearly as hard as steel, and 
almost infusible. Its specific gravity is 17.6. It 
takes fire when heated in the open air. 

174. — Manganesium. — Manganese was first ob- 
tained in a metallic state by the Swedish chemist, 
Gahn. It is found combined with oxygen in the 
form of a black oxide. It is a hard, brittle metal, 
of a grayish-white colour, and granular structure. 
Its specific gravity is 8.013. It is exceedingly infu- 
sible ; tarnishes by exposure to the air ; absorbs 
oxygen rapidly when heated to redness, and slowly 
decomposes water at common temperatures. 

175. Titanium. — Titanium was discovered by 



OSMIUM. 97 

Klaproth. It is found combined with oxygen in the 
mineral called rutile, or titanite. It has been ob- 
tained in the state of a deep blue-coloured powder, 
that takes fire in warm air. 

Metallic Titanium is also found in minute cubic 
crystals, in the slag of certain iron works. These 
crystals have a bright metallic lustre, and the colour 
of copper. Their specific gravity is 5.3. They 
scratch rock crystal, and are exceedingly infusible. 
Exposed to hot air, they become covered with a pur- 
ple film. 

176. Columbium. — Columbium was so called by 
its discoverer, Hatchett, who obtained it in 1S01, 
from a mineral found at New London, in Connecti- 
cut. Two years afterwards, Ekeberg obtained it 
from a Swedish mineral, and called it Tantalum. 
The identity of the two metals was proved by Wol- 
laston in 1809. 

Columbium is obtained in the form of a black 
powder that is a non-conductor of electricity, but 
which acquires a metallic lustre and an iron-gray co- 
lour, and becomes a conductor by pressure. It takes 
fire below redness, and burns with a vivid light. 
Its specific gravity and fusing point are not known. 

177. Uranium. — Uranium was obtained by Klap- 
roth in 1789, the year in which the planet Uranus 
was discovered, and received its name from this co- 
incidence. Its properties are imperfectly known. 
It has been obtained by conducting hydrogen gas 
over its protoxide heated in a glass tube. The sub- 
stance thus obtained, which was supposed to be me- 
tallic uranium, was crystalline, of a metallic lustre, 
and a reddish-brown colour. It suffered no change 
by exposure to air at common temperatures, but 
when heated, absorbed oxygen, and was reconverted 
into the protoxide. 

178. Osmium. — Osmium is found in native pla- 
tinum, from which it has been obtained in the state 

9 



98 PRINCIPLES OP CHEMISTRY. 

of a black powder, that acquires a metallic lustre by- 
friction. Its specific gravity varies from 7 to 10, ac- 
cording to its mode of preparation. It takes fire 
when heated in the open air, and is dissolved by- 
fuming nitrous acid. 

179. St annum. — Tin was known to the ancients. 
It is found combined with oxygen, and is procured 
from its ore by the aid of heat and charcoal. 

Tin has a white colour, and a lustre resembling 
that of silver, tarnishing very slowly by exposure 
to the air. It is so soft that it may be cut with an 
iron knife; it is inelastic and malleable. When bent 
backwards and forwards it emits a peculiar crackling 
sound. Its specific gravity is 7.2. At 442° it fuses, 
and its surface becomes covered with a gray pow- 
der. At a white heat it takes fire and burns with a 
white flame. It may be beaten into leaves of the 
thickness of the -ioVo^ 1 °f an inch- 

180. Aurum. — This metal has been known from 
the remotest antiquity. Gold is found in metallic 
grains among sand in the beds of rivers, and crystal- 
lized in octahedrons and cubes in rocky veins. 

It is the only metal of a yellow colour. Its spe- 
cific gravity is 19.257. It has a brilliant metallic 
lustre, which is not tarnished by the longest expo- 
sure to air and moisture. In ductility and mallea- 
bility it surpasses all other substances. A grain of 
gold may be extended so as to cover 52 square 
inches, with a thickness not exceeding - ¥ ^-._- of an 
inch, in which state it appears green by transmitted 
light. A grain of gold may also be drawn into a 
wire 550 feet long. Gold is very tenacious, though 
inferior in this respect to iron, copper, platinum, and 
silver. When pure it is exceedingly soft and flexi- 
ble. It fuses at 2016°, and is not oxidated by being 
kept for months in a state of fusion in an open ves- 
sel. By means of the oxyhydrogen blowpipe, or the 
galvanic battery, it may be set on fire, and burns 
with a greenish blue flame. 



PALLADIUM. 99 

Gold is readily dissolved by chlorine and fluorine. 

181. Platinum. — This metal is found in Brazil, 
Peru, and the Uralian Mountains. It was disco- 
vered by Ulloa, in 1705. Platinum occurs only in 
a metallic state, in the same localities with gold. 

Platinum is a metal of a white colour, which is 
less pure and brilliant than that of silver. It is, after 
iridium, the heaviest known substance, having a spe- 
cific gravity of 21.25. It is a very soft, malleable, 
and ductile metal, and like iron, admits of being 
welded at a high temperature. It is a less perfect con- 
ductor of heat than several other metals. Like gold 
it undergoes no change by exposure, for any length 
of time, to air and moisture, and it is not melted or 
oxidated in the strongest heat of an air furnace, 
although it is fused by galvanism and the oxyhydro- 
gen blowpipe. Chlorine is its only solvent. 

Platinum is precipitated from its solution in chlo- 
rine in the form of a gray metallic powder. This pow- 
der possesses the remarkable property of efFecting the 
inflammation of a mixture of hydrogen and oxygen 
gases. If a current of hydrogen gas be directed 
upon a small mass of this powder, it renders it red- 
hot, and soon takes fire. This property is possessed, 
in a less degree, by the thin leaf, the fine wire, and 
the filings of platinum, by gold, nickel, and several 
other metals. When the native platinum is digested 
in nitro chlorohydric acid, the solution is found to 
contain chlorides of platinum, palladium, and rho- 
dium, and there is left a black powder which consists 
of osmium, iridium, and other metals. 

182. Palladium. — This metal was discovered in 
1803, by Wollaston. It exists in small proportions 
combined with native platinum. 

It resembles platinum in colour and lustre, but is 
much harder and more fusible. It is ductile and 
malleable; its specific gravity is 11.3 to U.S. It is 
unalterable by exposure to air and moisture, and is 



100 PRINCIPLES OP CHEMISTRY. 

oxidized and dissolved, by nitric, sulphuric, and chlo- 
rohydric acids. 

183. Rhodium. — Rhodium was discovered by 
Wollaston, in 1S03. It exists in combination with 
native platinum. 

It is a brittle, extremely hard metal, of a white 
colour, with a specific gravity of about 11. It is not 
attacked, when pure, by any of the acids, and re- 
quires the strongest heat of a wind furnace for its 
fusion. 

184. Iridium.— -This metal is found in combina- 
tion with native platinum. It was discovered along 
with osmium in 1803, by Tennant. It is so brittle, 
that it falls to powder when burnished. Its colour 
is that of platinum, and it is the heaviest and most 
infusible of all the known metals. Its specific gravity 
has been recently determined by Dr. Hare to be 21.8. 
It is acted upon with difficulty by the acids, and when 
finely divided is oxidated at a red heat. 

185. Nickelum. — Nickel is found in combination 
with arsenic and sulphur, and is also a constituent of 
those masses of native iron, which are supposed to 
be of meteoric origin. 

It is highly ductile and malleable, has a brilliant 
metallic lustre, and a white colour intermediate be- 
tween tin and silver. Its specific gravity is 8.279, 
which rises to 9. when hammered. It is attracted 
by the magnet and is susceptible of permanent mag- 
netism, but loses this property at 630°. It is fusible 
with difficulty, and suffers no change by exposure to 
air and moisture at common temperatures. 

186. Argentum. — Silver was well known to the 
ancients. It is found native, and in combination with 
many other metals, and with sulphur. 

It is of a clear white colour, and exceeds all the 
pure metals in brilliancy. It is very soft, malleable, 
ductile, and tenacious. It crystalizes in octohedrons, 
and cubes. It may be beaten into leaves of the thick- 



BISMUTHUM. 101 

ness of T --L-^.th part of an inch, and drawn into a 
wire thinner than a human hair : a wire T ^-th of an 
inch in diameter will support 270 lbs. Its specific 
gravity is 10.474. to 10.51. It melts at a full red heat, 
and by an intense and long continued heat may be 
made to boil and evaporate away. Melted silver 
will absorb 22 times its volume of oxygen, with 
which it parts when becoming solid. In cooling from 
its fluid state, silver becomes covered with minute 
granulations in consequence of the escape of the oxy- 
gen, which it had absorbed. One or two per cent of 
copper destroys this property. It does not alter by 
exposure to air and moisture. In the galvanic cir- 
cuit and the oxyhydrogen blow pipe, silver burns 
with vivid scintillations, and a light green flame. 

Silver forms an insoluble compound with chlorine, 
which thus furnishes a ready test of its presence. It 
is dissolved freely by nitric acid. 

187. Hydrargyrum. — This metal was well known 
to the ancients. Mercury or quicksilver is found 
native in small quantities-, its principal ore is its 
combination with sulphur. 

It is distinguished from all other metals by its 
fluidity at the common temperature. It has a white 
colour like that of tin, and a brilliant metallic lustre. 
At — 39° or — 40°, it becomes solid, and in congealing 
has a tendency to crystalize in octohedrons. Solid 
mercury is malleable and ductile; its specific gravity 
is 15.612, while that of the fluid is 13.568. At 662° it 
enters into ebullition and evaporates. Mercury is 
not altered by exposure to air and moisture at com- 
mon temperatures. It is dissolved by chlorine, and 
by nitric and sulphuric acids. 

188. Bismuthum. — Although this metal was 
known to the ancients, it was confounded by them 
with tin and lead. Bismuth is found native, and in 
combination with sulphur, oxygen, and arsenic. 

It has a reddish-white colour, and considerable 
9* 



102 PRINCIPLES OF CHEMISTRY. 

metallic lustre. Its structure is highly lamellated, 
and it crystalizes in octohedrons and cubes. Its 
specific gravity is 9.8. It is brittle when cold, but 
may be hammered into plates when warm. At 476° 
it fuses, and at a red heat sublimes in close vessels, 
and burns with a bluish white flame in open ones. 
It conducts heat more slowly than most other metals. 
When fused it becomes covered with a gray film of 
oxide, and it is not much altered by exposure to air 
and moisture at common temperatures. 

189. Plumbum. — Lead was known to the an- 
cients. It is generally found combined with sulphur, 
in the ore called galena. 

It is of a bluish-gray colour, and a brilliant metal- 
lic lustre, which speedly tarnishes by exposure to the 
air. It is very soft, flexible, and non-elastic, and is 
ductile, and highly malleable. It is the least tena- 
cious of the ductile metals. Its specific gravity is 
11.381. It fuses at 612°, but does not sublime at a 
white heat. When cooled slowly it forms octohedral 
crystals. Lead absorbs oxygen quickly at high 
temperatures, and becomes covered with a film of 
oxide. 

190. Zincum. — Although the ancient Greeks and 
Romans were unacquainted with zinc, they used its 
ore, calamine, in the manufacture of brass. Zinc 
has long been known to the Chinese, but the method 
of extracting it from its ores was not known in Eu- 
rope till the middle of the eighteenth century. Zinc 
is found in combination with sulphur in the mineral 
called blende. 

It has a brilliant metallic lustre, a bluish-white 
colour, and a highly lamellated crystalline structure. 
Its specific gravity is 7. It is a hard metal, being 
acted upon with difficulty by the file. At low and 
high degrees of heat, it is brittle, but between 210° 
and 300° it is both malleable and ductile. It fuses 
at 773°, and when slowly cooled, crystalizes in four 



FERRUM. 103 

or six-sided prisms. In close vessels it sublimes un- 
changed at a white heat, and when, heated to a red 
heat, in a covered crucible, bursts into a flame when 
the cover is removed, burning with a brilliant white 
light, and being converted into a white flocculent 
powder. 

Zinc undergoes little change by the action of air 
and moisture, but is rapidly acted upon by diluted 
sulphuric acid. 

191. Cadmium. — Cadmium was discovered, by 
Stromeyer, in 1817. It is found in combination with 
the ores of zinc. 

It resembles tin in colour, lustre, and fusibility, but 
is harder and more tenacious. It is very ductile and 
malleable; its specific gravity is 8.604 to 8.694. It 
is nearly as volatile as mercury, and its vapour con- 
denses in globules of bright metallic lustre. It ab- 
sorbs oxygen in the open air, and is readily dissolved 
by nitric acid. 

192. Cuprum.^— Copper has been known from the 
earliest ages. It is found native and combined with 
sulphur. It is distinguished from all other metals, 
except titanium, by its red colour. It has a brilliant 
metallic lustre; it is ductile, malleable, highly tena- 
cious, hard, elastic, and sonorous. Its specific gravity 
is 8.895. It fuses at 1996° F. being more fusible 
than gold, and less so than silver. 

It is slowly oxidated by exposure to the air ; nitric 
acid acts upon it with violence. At a high tempera- 
ture copper takes fire and burns with a rich green 
flame. It is one of the best conductors of heat known ; 
melted copper volatilizes water so rapidly as to oc- 
casion dangerous explosions, when it is poured into 
vessels containing the smallest portion of moisture. 
It does not decompose water at any temperature. 

193. Ferrum. — Iron is the most abundant of all 
the metals; it is found in native masses of considera- 
ble magnitude, which are supposed to be of meteoric 



104 PRINCIPLES OF CHEMISTRY. 

origin. It is also found in combination with other 
metals, and with sulphur, and with oxygen, which 
last are its most abundant ores. 

It has a peculiar gray, or bluish-white colour, and 
a bright metallic lustre, which is much increased by 
polishing. It is very ductile and malleable, and the 
most tenacious of all the metals. Its specific gravity 
is 7.7; its texture is fibrous, and it requires for its 
fusion the highest temperature of the wind furnace. 
At common temperatures it is very hard and unyield- 
ing, but at a red heat it becomes very soft and plia- 
ble, so that two pieces may be incorporated or welded 
together by hammering. It is attracted by the mag- 
net, and may be rendered permanently magnetic. 
It is rusted or oxidated by exposure to the air and 
moisture; and is rapidly dissolved by dilute sul- 
phuric acid. Iron is the only metal which takes fire 
by collision with flint. It becomes hot, and may be 
heated to a red heat by percussion. It burns with 
vivid scintillations in oxygen gas, and a bar of iron 
heated to a full white heat, may be made to burn in 
the open air by rapidly whirling it round. A circu- 
lar disc of soft iron, made to revolve in a lathe, will 
cut the hardest steel, without being itself worn 
away. 

When it is first obtained from its ores in the form 
of cast iron, it contains many impurities, such as 
carbon, and other metals. Cast iron fuses much more 
readily than pure iron, and acquires a granular tex- 
ture in cooling. There are two kinds, the white and 
the gray ; of which the former is exceedingly brittle, 
and the gray more soft and tenacious. The differ- 
ence between them appears to be owing to changes 
dependent upon the rapidity of their cooling; for the 
former is converted into the latter by being strongly 
heated and slowly cooled. 

When bars of the purest malleable iron are exposed 
for several days to a full red heat in contact with 



ALUMINIUM. 105 

powdered charcoal, they are converted into steel, a 
substance intermediate between pure and cast iron. 
It contains 1.3 to 1.75 per cent of carbon, is far in- 
ferior in ductility and malleability to pure iron, but 
greatly exceeds it in sonorousness, hardness, and 
elasticity. Its texture is more compact, and it is 
susceptible of the highest polish. It is more fusible 
than pure, and less so than cast iron, and forms cast 
steel by fusion. 

Although cast iron and steel do not belong to the 
class of simple elements, yet the modifications they 
exhibit of the properties of iron are so slight as to 
render it most convenient to treat of them in this 
place. 

194. Cobaltum. — Cobalt was discovered in 1733, 
by a Swedish chemist, named Brandt. It derives its 
name from Kobold, an evil spirit — a term applied to 
its ore by the German miners, before they were ac- 
quainted with its value. 

Cobalt is a brittle metal, of a reddish-gray colour, 
a granular and sometimes lamellated structure, and 
feeble metallic lustre. It fuses below the melting 
point of iron, and crystalizes in irregular prisms by 
slow cooling. Its specific gravity is 7.834; it is 
feebly, but permanently, magnetic; it is slowly oxi- 
dized by heat and air, and burns in the oxyhydro- 
gen blowpipe with a rich red or purple flame. 

195. Cerium, Lantanium. — Cerium, named after 
the planet Ceres, was discovered by Berzelius, in a 
rare Swedish mineral; and Lantanium has recently 
been discovered in the same mineral by Mosander. 
Very little is known of their properties. Cerium has 
been obtained in minute grains as large as a pin's 
head, and is a white brittle metal. 

196. .Aluminium. — Aluminium is the metallic 
base of alumina, one of the most abundant of the 
earthy oxides. 

It is obtained in the form of a gray powder, or 
small scales of the lustre and colour of tin. It re- 



106 PRINCIPLES OF CHEMISTRY. 

quires a greater heat than cast iron does, to fuse it. 
When heated to redness in the open air, in oxygen, 
or in chlorine gas, it takes fire and burns with a very- 
vivid light. It is malleable and ductile, and is not 
tarnished by exposure to air and moisture at common 
temperatures. 

197. Yttrium.— Yttrium is the metallic base of an 
earth found at Ytterby, in Sweden, and called from 
that circumstance Yttria. 

Yttrium has been obtained in the form of metallic 
scales, of a grayish-black colour, and metallic lustre. 
It is brittle, and burns with splendour when heated to 
redness in atmospheric air. 

198. Glucinium. — Glucinium is the metallic base 
of an earth called glucina, which has hitherto been 
found only in a few rare minerals, of which the 
emerald is the best known. Glucinium has been ob- 
tained in the form of a grayish-black powder, which 
acquires a dark metallic lustre by burnishing. It is 
not oxidised by exposure to air and moisture, but 
takes fire at a red heat in atmospheric air and in 
chlorine, and burns with great splendour. 

199. Thorium* — Thorium is the base of an earth 
which has been found in a rare Norwegian mineral 
called thorite. It resembles glucinium in its proper- 
ties. 

200. Zirconium. — Zirconium is the base of the 
earth zirconia. It has been obtained in the form of 
metallic scales, although little is known of its pro- 
perties. 

201. Magnesium. — Magnesium is the base of the 
alkaline earth magnesia. 

It has a brilliant metallic lustre, a white colour 
like silver, is very malleable, and fuses at a red heat. 
It is superficially oxidated in a moist atmosphere, but 
undergoes no change in dry air, or by boiling with 
water. It inflames spontaneously in chlorine, and 
burns brilliantly when heated to redness in the open 
air. 



POTASSIUM. 107 

202. Calcium. — Calcium is the metallic base of 
lime, and is a metal of a white colour, whose other 
properties are unknown. 

203. Strontium. — Strontium is the metallic base 
of the earth, strontia ; very little is known of its pro- 
perties. 

204. Barium. — Barium is the base of the earth 
baryta. 

It is a metal of a dark gray colour, with a lustre 
inferior to that of cast iron. It sinks rapidly in strong 
sulphuric acid, and attracts oxygen with avidity from 
the atmosphere. It rapidly decomposes water, which 
it causes to effervesce strongly by the disengagement 
of hydrogen gas. 

205. Lithium. — Lithium is the metallic base of 
an alkali, called lithia, which enters into the compo- 
sition of the mineral petalite, and of several varie- 
ties of mica. It is a white metal, and little is known 
of its properties. 

206. Sodium. — Sodium is the metallic base of the 
alkali, soda. Its combination with chlorine is com- 
mon salt. 

Sodium has a strong metallic lustre, and resembles 
silver in colour. It is so soft and ductile at common 
temperatures, that it may be moulded into any shape 
with the fingers. It fuses at 200°, and volatilizes at 
a red heat. Its specific gravity is .972. 

It speedily tarnishes by exposure, and is instantly 
oxidated by water. When the water is warm, the 
sodium takes fire in consequence of the heat which 
is disengaged, and burns vividly. 

207. Potassium. — Potassium is the metallic base 
of the common vegetable alkali, potassa. 

It was discovered in 1807, by Sir Humphrey Davy, 
who decomposed potassa by means of a powerful 
galvanic battery, in the commencement of those ce- 
lebrated investigations, which led to the discovery of 
the metallic bases of the other alkalies and earths. 



108 PRINCIPLES OF CHEMISTRY. 

Potassium is solid at the ordinary temperature. 
At 70° it is somewhat fluid, and becomes perfectly 
so, at 150.° At 50° it is soft like wax, and yields to 
the pressure of the finger. At 32° it becomes brit- 
tle. Its texture is crystalline; in colour and lustre 
it resembles mercury, and its specific gravity is .865. 
It is opaque, and conducts heat and electricity. 

Its affinity for oxygen is so strong, that it rapidly 
oxidizes in the air, and must therefore be preserved 
in glass tubes hermetically sealed, or under naphtha, 
or some other liquid which does not contain oxygen. 
When heated, in the open air, it takes fire and burns 
with a purple flame. It decomposes water on the 
instant of touching it, and so much heat is disen- 
gaged, that the potassium takes fire, and burns vivid- 
ly, at the same time inflaming the hydrogen gas 
which is disengaged. 

When plunged under water, a violent reaction 
takes place without light, and pure hydrogen gas is 
evolved. 



CHAPTER II. 

OF COMBINATION. 

208. The simple substances described in the last 
chapter, are the elements from which, in virtue of 
their mutual affinity, are formed all the various com- 
pounds in nature. 

209. Constitution of Bodies. — A compound sub- 
stance, so long as it retains the same properties, 
always consists of the same elements united in the 
same proportions. This is the essential law of che- 
mical affinity, and is the only certain foundation of 
the science of Chemistry. Water, as we have seen, 
is a compound of oxygen and hydrogen. It is evi- 



LAW OF DEFINITE PROPORTIONS. 109 

dent that there must be a limit below which the 
mechanical division of a drop of water cannot be 
carried, and that it must be possible, by repeated 
subdivisions, to arrive at this point. If we could 
by any means divide this particle, it is evident that 
we should obtain — not two particles of water, but 
those of oxygen and hydrogen, by the union of 
which water is formed. It is to these ultimate par- 
ticles of bodies, which must necessarily exist, that 
we give the name of atoms. Whether they are ac- 
tually the ultimate physical atoms, or lowest actual 
subdivision of particles, we cannot tell; but they are 
ultimate atoms so far as the chemist is concerned, 
although, in the case of the simple elements, they 
may consist of a number of physical atoms cohering 
in crystalline groups. When we speak of the atoms 
of a body, therefore, we must be understood as mean- 
ing the ultimate particles of compound bodies only. 
210. Law of Definite Proportions. — When we 
attempt to combine the various simple elements, and 
to ascertain the proportions in which they unite, we 
arrive at several very remarkable results. Let us 
take, for example, the elements oxygen, sulphur, 
iron, potassium, and chlorine. Eight parts by weight 
of oxygen unite with 16.1 parts of sulphur, with 2S 
of iron, with 39.15 of potassium, and with 35.42 
of chlorine, to form definite chemical compounds. 
Twenty-eight parts of iron combine in the same 
way, with 16.1 of sulphur, with 39.15 of potassium, 
and with 35.42 of chlorine; 16,1 of sulphur, with 
39.15 of potassium, and 35.42 of chlorine; and 39.15 
of potassium, with 35.42 of chlorine. The quantity 
of each of the other simple elements which combines 
with eight parts by weight of oxygen, will also com- 
bine with and neutralize the same quantity of all 
the others which oxygen does; so that we are thus 
furnished with a series of numbers, representing the 
proportions in which the simple elements combine, 

10 



] 10 PRINCIPLES OF CHEMISTRY. 

and therefore, with propriety, called their combining 
numbers or their chemical equivalents. 

211. Law of Multiple Proportions. — In many 
instances, there are several combinations in different 
proportions of the same elements. Thus there are 
five compounds of oxygen with nitrogen, and two 
with iron. In all such cases the proportions of the 
several elements vary by a very simple law. It 
commonly happens that one only of the elements is 
increased in quantity, and this always increases by 
a simple multiple. Thus in the several compounds 
of oxygen and nitrogen, that in which there is the 
least oxygen consists of 8 parts by weight, of oxy- 
gen and 14.15 of nitrogen. The second consists of 
16, the third of 24, the fourth of 32, and the fifth of 
40 parts of oxygen, to the same quantity 14.15 of 
nitrogen. On the other hand, the first combination 
of iron with oxygen, contains 28 of iron and 8 of 
oxygen; and the second 28x2=56 of iron, and 8x3 
=24 of oxygen. The lowest of these combinations 
must be conceived to consist of a chemical atom of 
oxygen, united with one of nitrogen, or of iron; while 
the others contain 2, 3,4 or 5 atoms of oxygen united 
with one of nitrogen, or 3 atoms of oxygen with two 
of iron. 

The views above given of the definite nature of 
chemical compounds, receive the strongest confirma- 
tion from the laws which regulate the union of gases. 
All the known gases combine either in equal volumes, 
or in volumes which are in the simple ratio of 1 to 
2, 1 to 3, 1 to 4, 2 to 3, 2 to 5, &c, nor can they be 
made to unite in any intermediate fractional ratio. 
For example, 50 measures of oxygen unite with 100 
measures of hydrogen to form water; 100 measures 
of nitrogen unite with 50 of oxygen to form pro- 
toxide of nitrogen, and with 250, to form nitric acid. 
212. Equivalent Numbers. — These combining 
numbers represent not only the composition of these 



EQUIVALENT NUMBERS. Ill 

compounds, but the proportions in which they them- 
selves unite to form more complex combinations. 
Thus five atoms of oxygen and one of nitrogen form 
the substance called nitric acid, the combining num- 
ber of which is the sum of the weights of its ele- 
ments, that is 5x8+14. 15.=z54. 15. One atom of 
oxygen, and one* of potassium, form the substance 
called potassa, the combining number of which is 
47.15; and one atom of nitric acid and one of pot- 
assa, unite to form the salt called nitrate of potassa, 
the atomic weight or combining number of which 
is 54.15+47.15=101.3. This law applies to the 
most complex combinations. The combining or 
atomic weight of any substance whatever, is the 
sum of the weights of the simple atoms that com- 
pose it; and these numbers, or their multiples, express 
in all cases, the proportions in which the bodies 
combine. 

213. The lowest combination of oxygen with iron, 
is in the proportion of 8 to 28, and the next highest, 
of 12 to 28. If we regard 8 as the weight of an 
atom of oxygen, 12 must represent an atom and a 
half, which is manifestly an impossible quantity. It 
is found likewise, that when this oxide enters into 
combination, its combining number is 80, and not 40; 
and we must therefore suppose that it is formed of 
three atoms of oxygen and two of iron. 

214. There is a combination of sulphur and oxy- 
gen (the hypo-sulphurous acid) in the proportions of 
16.1 to 8, and of which the combining number 
might be supposed to be 24.1. It is found that this 
acid unites with a single atom of oxides to form 
salts, and that its combining number is always 48.2, 
and not 24.1. It is therefore inferred, that it is a 
compound of two atoms of each of its elements. 
These examples prove that the actual combining 
number of a body cannot be ascertained from mere 
theory, without ascertaining the fact from experi- 
ment. 



112 PRINCIPLES OF CHEMISTRY. 

215. Proximate and Ultimate Elements. — It is 
easy to determine the proportions of the simple ulti- 
mate elements that enter into the composition of a 
complex body. It is far otherwise when we attempt 
to ascertain the nature of the proximate elements, 
as they are termed, of these compounds. What, for 
example, is the true constitution of the salt called 
nitrate of potassa? It is formed, as we have seen, 
by the union of nitric acid with potassa; and we 
may conceive these to be its proximate elements; or 
we may imagine the six atoms of oxygen, the atom 
of nitrogen, and that of potassium which it contains, 
to be combined in various other ways, so as to ren- 
der it, theoretically, a substance belonging to an en- 
tirely different class. So, likewise, there is a salt 
which contains six atoms of oxygen, one of nitrogen, 
and one of lead. Now we may conceive this salt to 
be the nitrate of the protoxide of lead, (Pb O+NO 5 ), 
or the nitrite of the deutoxide, (Pb0 2 +N0 4 ), or it 
may be, as is now supposed by many, a combination 
of metallic lead, with a radical consisting of one 
atom of nitrogen and six of oxygen (Pb+N0 6 ). The 
speculations into which this uncertainty has led, 
constitute one of the most subtle and refined inves- 
tigations in the science, and will be hereafter re- 
verted to. 

216. Isomerism. — This subject has presented it- 
self to chemists in another aspect. Several sub- 
stances have been discovered, possessing properties 
so different from each other, as to create no suspicion 
of their identity. Yet analysis has proved them to 
consist of the same ultimate elements united in the 
same proportions. It might be thought at first sight, 
that a single fact of this kind would unsettle the 
science, by destroying the value of sensible proper- 
ties as a test of identity of composition. 

A closer examination shows that it is a natural 
result of a complex combination. The ultimate ele- 
ments must be capable of forming various simpler 



WEIGHTS OF THE ELEMENTS. 113 

compounds, which are themselves the proximate 
elements of the bodies into which they enter, and 
thus, under an apparent identity, conceal an essen- 
tial difference of composition. This resemblance is 
called Isomerism, and those bodies are said to be 
isomeric, the sensible properties of which differ, 
while their ultimate composition and combining 
numbers are the same. 

217. There is a compound of carbon and hydro- 
gen in their atomic proportions, but which consists 
undoubtedly of two atoms of each of its elements. 
This is the olefiant gas of chemists, and its combin- 
ing number is 6.12+1X2=14.24. There is another 
substance called etherine, entirely distinct in its pro- 
perties, composed of the same elements in the same 
proportions; but of which the combining number 
is found to be 28.48; being composed of four atoms 
of each of its elements. There are many examples 
of the modified isomerism, of which this is an in- 
stance. 

218. Atomic Weights of the Elements. — The fol- 
lowing table contains the names and atomic weights 
of the simple elements, and the characters by which 
they are expressed in designating their various com- 
pounds. The numbers are taken from the last edi- 
tion (1841) of Turner's Chemistry, by Liebig and 
Gregory. 

Elements. Symbols. At. Num. Elements. 

Oxygen, O. 8. Phosphorus, 

Chlorine, CI. 35.42 Selenium, 

Iodine, ' /. 126.3 Tellurium, 

Bromine, Br. 78.4 Arsenic, 

Fluorine, F. 18.68 Antimony, 

Nitrogen, N. 14.15 (Stibium,) 

Hydrogen, H. 1. Chrome, 

Carbon, C. 6.12 Vanadium, 

Boron, B. 10.9 Molybdenum, Mo. 47.7 

Silicon, Si. 22.5 

10* 



Symb. 


Jit.JV. 


P. 


15.7 


Se. 


39.6 


Te. 


64.2 


rfs. 


37.7 


St. 


64.6 


Cr. 


28. 


V. 


68.5 



114 



PRINCIPLES OF CHEMISTRY. 



Elements, 

Sulphur, 
Columbium, 

(Tantalum,) 
Uranium, 
Cobalt, 
Manganese, 
Titanium, 
Stannum, 
Aurum, 
Platinum, 
Argentum, 
Palladium, 
Rhodium, 
Osmium, 
Iridium, 
Nickel, 

Hydrargyrum, 
Bismuth, 
Plumbum, 
Cuprum, 



Symbols. Jit. Numb, Elements. Symbols. At. Numb. 

S. 16.1 Tungsten,] 

(Wolfram,) W. 



Ta. 185. Zinc, 
U. 217. Cadmium, 
Co. 29,5 Ferrum, 
Mn. 27,7 Cerium, 
Ti. 24.3 Aluminium, 
Sn. 57,9 Yttrium, 
Jiu, 199.2 Glucinium, 



Zn 

Cd, 

Fe. 

Ce. 

Al. 

Y. 

G. 

Th, 
Zr. 

Mg, 

Ca, 

Sr. 

Ba. 

L, 



99.7 
32.3 
55.8 
28. 
46. 
13.7 
32.2 
26.5 
59.6 
33.7 
12.7 
20.5 
43.8 
68.7 
6. 



PI. 98.8 Thorium. 

Jig, 108. Zirconium, 

Pd. 53.3 Magnesium, 

R. 52.2 Calcium, 

Os. 99.7 Strontium, 

Ir. 98.8 Barium, 

Ni. 29.5 Lithium, 

Hg. 202. Sodium, 

Bi, 71. (Natrium) Na. 23.3 

Pb, 103.6 Potassium, 

Cu. 31.6 (Kalium.) K, 39.15 
The numbers above given are entitled to as much 
confidence as the state of experimental science will 
warrant; althoughslightdifFerenceswillarisein calcu- 
lating the result of different analyses. The only varia- 
ations which it is important to notice, are, that Berze- 
lius, and other Continental chemists, supposing the 
same volume of all simple gases to consist of the same 
number of atoms, regard the atomic weight of hydro- 
gen, nitrogen, chlorine, bromine, iodine, and fluorine, 
as only half that above stated, and give the atomic 
constitution of bodies, at double the number of atoms 
of these elements, which the English chemists assign. 
Other chemists, from theoretical views, double the 
atomic numbers of phosphorus, arsenic, and anti- 
mony, and halve that of Mercury. 

219. Chemical Symbols, — There are two me- 
thods of using the symbols in the preceding table. 



CHEMICAL SYMBOLS. 115 

The first, or algebraic mode, will be readily under- 
stood by a few examples. Thus the several com- 
pounds of nitrogen and oxygen are designated by 
N+O, N+20, N+30, N+40, N+50, the figures 
denoting then umber of atoms. Thus Fe+O, and 2 
Fe+30, denote the protoxide, and sesqui-oxide of 
iron. The formula, (N+50)+(2 Fe+30), denotes the 
nitrate of the sesqui-oxide of iron, and (K+0)+2 
(S+30), the bisulphate ofpotassa. The advantages 
of the algebraic method are its simplicity and exact 
representation of facts. It is, however, inconveni- 
ently long, and Berzelius has introduced several 
modifications which are recommended by their bre- 
vity. He expresses the degree of oxidation by dots 
placed over the symbol, and the number of atoms of 
sulphur by commas placed in like manner, and he 
represents two atoms of base by a dash, through or be- 
neath its symbol. Thus the following algebraic sym- 
bols N+O, N+20, N+30, N+40, Fe+S, Fe+2S, 2 
Fe+30, would be represented by Berzelius thus: 

N, N, N, N, Fe, Fe, and Fe. 

220. A more convenient method, which is now 
becoming general, and which will be adopted in this 
volume, will be best understood by examples. The 
symbols are written without any intervening sign, 
and the number of atoms of each element is desig- 
nated by figures placed at the foot, and to the right of 
the proper symbol. Thus NO, N0 2 , N0 3 , N0 4 , 
N0 5 , Fe 0, Fe 2 3 , designate the several oxides 
of nitrogen and iron above mentioned. The proper 
numeral is prefixed to designate the number of the 
atoms of these compounds, which unite to form com- 
pounds of a secondary order, and the sign of addi- 
tion, or a simple comma connects the symbols; as 
KO+2SO3, KO, 2SO3 for the bi-sulphate ofpot- 
assa. 

There are many compounds of a very complex 



116 PRINCIPLES OF CHEMISTRY, 

constitution, the occurrence of which as an element 
of other bodies is so frequent, that a distinct symbol 
is used to express them. Thus, for instance the 
composition of Benzule is C 14 H 5 2 , and its sym- 
bol is Bz. Water, ammonia, and other compounds, 
which enter extensively into combination, have also 
distinct symbols, which will be noticed in the several 
cases as they occur. 

221. Chemical Nomenclature. — The rapid ad- 
vances which the science of chemistry has made 
within the last sixty years is undoubtedly due, in a 
great measure, to the nomenclature framed by the 
illustrious Lavoisier, and his associates, Guy ton Mor- 
veau, Berthollet, and Fourcroy. It is the most 
beautiful example of an universal philosophical lan- 
guage, which has ever been presented to the world, 
and it has greatly aided the diffusion of accurate 
chemical knowledge, by the perfect precision and self- 
explaining character of its terms. 

Even in those cases in which the sagacious fra- 
mers of this language fell into theoretical errors, 
from the imperfect state of chemical science in their 
day, the principles which guided them, furnish us 
with the means of rectifying their errors and supply- 
ing their defects. 

222. The following is a sketch of the nomencla- 
ture at present in use. 

The bi-elementary compounds are arranged in 
genera named from the electro-negative element, by 
adding to it the termination ide or uret. Thus the 
compounds oxygen, chlorine, bromine, iodine and 
fluorine, are called oxides, chlorides, bromides, iodi- 
des, and fluorides, and the compounds of carbon, 
sulphur, phosphorus, hydrogen, are called carburets, 
sulphurets, phosphurets, and hydrogurets. 

As the same substances unite in more than one 
proportion, the various compounds are designated by 
terms explanatory of their composition. A com- 



ACIDS. 117 

pound formed by the union of an atom of each of its 
elements, is called a protoxide, a proto-chloride, &c., 
or simply an oxide, chloride, &c, as the case may be. 
If it consists of two, three, or four atoms of the elec- 
tro-negative element united with one of the electro- 
positive, it is called deuto or bi-chloride, deutoxide 
or binoxide, ter-chloride, ter-oxide, quadrochloride, 
quadroxide, &c. The combination which contains 
the greatest portion of the electro-negative element, 
is also called a per-oxide, per-chloride, &c. 

If the compound contains three atoms of the elec- 
tro-negative and two of the electro-positive element, 
it is called a sesqui-oxide, sesqui-chloride, &c. 

If it contains one atom of the electro-negative ele- 
ment, united with two, three, or four atoms of the 
electro-positive, it is called a rfz-chloride, tri-chlo- 
ride, &c. 

It has not been deemed necessary to extend this 
system of nomenclature further than is here pointed 
cfut. When bi-elementary combinations of a greater 
number of atoms do however occur, they may be 
designated by fractional numbers in which the nu- 
merator represents the electro-negative, and the de- 
nominator the electro-positive element, as, for exam- 
ple, the | oxide of iron would designate a com- 
pound of 4 atoms of oxygen with 5 of iron. 

223. These bi-elementary compounds are them- 
selves elements of a secondary order, divided into 
acids and bases, and forming, by their union with 
each other, several distinct and peculiar classes of 
compounds, the most important and extensive of 
which is that of the neutral salts. 

224. Acids. — An acid, in the meaning attached by 
Lavoisier, and his associates, to that term, is an oxide 
having a sour taste, reddening vegetable blues, and 
combining with the alkalies and earths, so as to form 
a transparent crystalline compound, termed a salt. 
But many substances which possess all these pro- 



118 PRINCIPLES OF CHEMISTRY. 

perties contain no oxygen* and others which form 
neutral salts have not a sour taste and do not redden 
vegetable blues. It has therefore become necessary 
to extend the meaning of the term acid, and to in- 
clude in the class all those electro-negative com- 
pounds which combine with the electro-positive com- 
pounds of the same genus, and form crystalline 
compounds analogous to the salts. 

The simple electro-negative elements, oxygen, 
chlorine, iodine, bromine, fluorine, sulphur, and se- 
lenium, combine with the elements which are electro- 
positive in relation to them, forming compounds 
which are either electro-negative or electro-positive. 
The former constitute, as has been said, the class of 
acids. 

Instead therefore of oxygen being, as Lavoisier 
supposed, the sole principle of acidification, we have 
oxygen acids, chlorine acids, iodine acids, &c, each 
constituting a separate genus of acids. It was early 
discovered that the same substance formed more than 
one acid, as, for example, there are two acids of sul- 
phur, two of nitrogen, and two of phosphorus. In 
order to distinguish these from each other, Lavoisier 
designated thatacid which contains the smallest quan- 
tity of oxygen, by adding to the name of the base the 
termination ous, and the other by the termination ic, 
as sulphurous, nitrous, phosphorous, sulphuric, nitric 
and phosphoric acids. Acids have since been dis- 
covered intermediate between the above, or of still 
lower degrees of oxygenation. These acids have 
been designated by prefixing the term hypo to the 
name of the acid following them in the series of oxy- 
genation. Thus hypo-nitrous, and hypo-nitric acids, 
contain less oxygen than the nitrous, and nitric acids, 
and immediately precede them in the series of oxy- 
genation. 

225. While it was supposed that oxygen was the 
sole acidifier, the above nomenclature was sufficient 



SALTS. 119 

for all the cases that could occur. But as there are 
other acidifiers than oxygen, each forming acids with 
the same base, it has become necessary to designate 
the acidifying principle. Hydrogen, for example, 
forms acids with chlorine, iodine, bromine, sulphur, 
&c, which are designated by the terms chloro-hydric, 
iodo-hydric, bromo-hydric, and sulpho-hydric acids. 
Carbon is another example of this, as it is acidified 
both by oxygen and sulphur. The two acids are 
therefore to be called the oxy-carbonic and the sul- 
pho-carbonic acids ; but inasmuch as the oxygen 
acids are the most numerous and abundant, and as 
long use has familiarized us to their name, we seldom 
prefix to them the term oxy, but always understand 
an oxygen acid to be spoken of when the name of 
the base only is given. 

226. Bases. — The electro-positive bi-elementary 
compounds are classed together under the name of 
bases, and possess the common property of forming 
salts by combining with, and neutralizing the acids 
of the same genus; that is to say, the electro-positive 
oxides, and sulphurets, combine with electro-negative 
oxides, and sulphurets, forming oxygen, and sulphur 
salts. 

227. Salts. — Chlorine, iodine, bromine and fluo- 
rine, combine with the metals, and these binary com- 
pounds are genuine salts. Berzelius distinguishes 
them by the name of haloid salts. The bearing of 
this fact upon the true theory of the oxygen salts 
will be hereafter noticed. At present it will suffice 
to give the Levoisierian view of their constitution. 

As Lavoisier knew of but one class of acids, he 
was acquainted with but one class of salts, and in 
framing his nomenclature did not provide for the 
designation of any but oxy-salts. 

Each distinct acid forms and gives its name to a 
peculiar genus of salts. The salts formed by the 
acids whose names terminate in ous are designated 



120 PRINCIPLES OF CHEMISTRY. 

by the termination ite. Thus the salts formed by 
the sulphurous, phosphorous, nitrous, and arsenious 
acids, are called sulphites, phosphites, nitrites, and 
arsenites of the several bases ; as the sulphite of iron, 
copper, &c. The salts formed by the acids whose 
names terminate in ic, are designated by the termi- 
nation ate; thus the salts formed by the sulphuric, 
carbonic, nitric and arsenic acids are termed the sul- 
phates, carbonates, nitrates, and arseniates of their 
several bases, as the sulphate of iron, copper, &c. 

228. The number of atoms in the electro-negative 
element of a salt is designated by the Latin nume- 
rals. Thus the terms bi, ter, and sesqui sulphate of 
iron, denote a combination of 2, 3, and 1 j atoms of 
sulphuric acid, with an atom of oxide of iron. As 
many of the metals form more than one compound 
with electro-negative elements, and thus furnish 
more than one saline base, it is necessary to desig- 
nate these in the nomenclature of the salts. This 
can generally be done with great accuracy by using 
the terms proto, deuto, and per, to designate the first, 
second, and highest combinations of the metals, with 
an electro-negative element. Thus the proto-sul- 
phate of iron, and the per-sulphate of iron, denote 
the combination of sulphuric acid witnthe protoxide, 
and per-oxide of iron ; and the bi-proto-sulphate, and 
the bi-per-sulphate of iron denote the combination 
of two atoms of the acid with an atom of the respec- 
tive bases. 

229. When we wish to designate the class to 
which a salt belongs, we must prefix the name of 
the class; thus, for example, the oxy-sulphate of 
iron denotes a salt in which the teroxide of sulphur 
(sulphuric acid) is combined with the protoxide of 
iron. 

A sulphur salt is, in the same manner, the combi- 
nation of an electro-negative sulphuret, with an elec- 
tro-positive one. The bi-sulphuret of carbon, and 



ELECTROLYTIC DECOMPOSITION. 121 

the per-sulphuret of arsenic, are sulphur acids, whose 
correct names are sulpho-carbonic, and sulph-arsenic 
acids, and their combinations with electro-positive 
sulphurets, are the sulpho-carbonates and sulph-ar- 
seniates. 

230. Electrolytic Decomposition. — It is observed 
that when any compound substance whatever is de- 
composed in the voltaic circuit, one of its elements is 
separated at the positive, and the other at the nega- 
tive electrode. It is therefore inferred, that all sub- 
stances that enter into combination are in opposite 
electrical states, one of them being negative and the 
other positive. The laws which regulate the chemi- 
cal action of the voltaic battery, are therefore calcu- 
lated to throw much light on the nature of chemical 
forces. 

23L It has been ascertained by Dr. Faraday, that 
no substance that is a non-conductor of electricity is 
either capable of exciting electrical currents in the 
battery, or susceptible of electro-chemical decompo- 
sition; or, in other words, this cannot take place un- 
less an electrical current is transmitted through the 
substance. 

As the solidity of a body prevents that mobility of 
its particles which is necessary to its decomposition, 
and as no electrical current can pass in the voltaic 
circuit without decomposition, it is evident that the 
exciting body in a circuit must be in a fluid state. 
Accordingly it is found that ice will not conduct the 
electric current and is not susceptible of decomposi- 
tion, and the observation holds true of all other solids 
that are capable of exciting the voltaic battery in 
their liquid state. 

232. Faraday further ascertained that of all the 
various combinations of any two elements, one only 
is susceptible of electro-chemical decomposition, and 
that this in all cases consists of an equal number of 
atoms of each element. Bodies susceptible of elec- 

11 



122 PRINCIPLES OF CHEMISTRY. 

tro-chemical decomposition are called electrolytes, 
which are therefore in all cases binary compounds. 
To electrolyse a body, is to decompose it by the di- 
rect action of electricity; the name being compound- 
ed of i}%£xi!gov, and a/uco, to loose. 

233. The elements of an electrolyte are called 
ions, from iov, going. Anions are those ions which 
appear at the anode, and cations those which appear 
at the cathode. 

It is ascertained that most, and it is probable that 
all, of the simple elements are ions. Owing to the 
difficulty of obtaining liquid electrolytic compounds 
of nitrogen, carbon, phosphorus, boron, silicon, and 
aluminium, these elements have not yet been proved 
to be ions. 

An ion is not necessarily a simple body, for any 
compound substance forming a binary compound 
with another becomes an ion. Those neutral salts, 
for example, which contain an atom of acid and an 
atom of alkali, are all electrolytes, and their elements 
ions, although none of the acids are themselves elec- 
trolytes. 

234. Many substances not electrolytes are them- 
selves decomposed by what is called the secondary 
action of the battery. The elements of the decom- 
posed electrolyte being set free, are presented in 
their nascent form to the adjacent bodies, a circum- 
stance peculiarly favourable to chemical action. Ni- 
tric acid is thus decomposed by the hydrogen of the 
water which is set free; and nitrous acid and water 
are formed. In many cases the electrode itself is at- 
tacked, as when zinc, for example, is used, it is oxi- 
dated by the nascent oxygen of the water. 

In experiments with the voltaic battery this secon- 
dary action of the pile must be carefully separated 
from its primary and direct action. The former adds 
nothing to the quantity or intensity of the electrical 
currents set in motion by the latter. 



THE VOLTA ELECTROMETER. 123 

235. The Volt a Electrometer. — It has been clear- 
ly ascertained by Faraday, that these currents are an 
exact measure of the quantity of the electrolytic 
action of the pile. By using electrodes of platinum 
and pure zinc, he obtained a battery in which there 
was no chemical decomposition, except that which 
was owing to electrolytic action, and he was thus 
enabled to ascertain its exact amount. By conduct- 
ing the electrical currents thus produced through a 
vessel of water, and collecting the gases resulting 
from its decomposition, he proved that the quantity 
of water decomposed by the electrical current was 
precisely equal to that, the decomposition of which, 
in each cell of the battery, set the current in motion. 
He also discovered that the same current may be 
made to perform any number of decompositions, 
and was thus enabled to submit various compounds 
at the same time to the action of the same current, 
and proved that the quantities thus decomposed 
were always in the exact ratio of their atomic weight. 
The current which decomposed 9 grains of water 
(HO=9), also decomposed 230 grains of iodide 
of lead (1 iodine=126.3+l leadz=103.6) and 143.42 
grains of chloride of silver (1 chlorine=35.42+l sil- 
verz=108); that is to say, the electricity evolved by 
the electrolytic decomposition of an atom of water 
is exactly sufficient to decompose an atom of any 
other electrolyte. By the aid of a simple instrument 
called the volta electrometer, which consists of pla- 
tinum electrodes inserted in a graduated glass tube, 
in which the gases evolved by the decomposition of 
water are collected, he obtained a measure of the 
quantity of electricity that had passed through the 
voltaic circuit in a given interval of time. We are 
thus furnished with a means of measuring electricity 
by its chemical agencies, as accurately as we mea- 
sure the relative degrees of heat by the thermo- 
meter. 



124 PRINCIPLES OF CHEMISTRY. 

236. Identity of Chemical and Electrical Forces. 
— It appears probable that when a compound is de- 
composed by electricity, the positive electricity of 
the current combines with the negative electricity of 
the negative element, and the negative electricity of 
the current with the positive electricity of the posi- 
tive element. The forces which held the two ele- 
ments together are thus neutralized, and the infer- 
ence seems irresistible that they must be the antago- 
nist forces, or, in other words, the opposite electricities 
of those by which they are thus counteracted. If, 
therefore, the elements that form compound bodies 
are held together by electrical forces, and are sepa- 
rated when these forces are neutralized by an equal 
quantity of the opposite electricity, it is evident that 
the same quantity of electricity must be the agent 
in holding together an atom of any binary compound 
whatever, for an atom of such compound is always 
decomposed by the quantity of electricity that is 
evolved in the electrolytic decomposition of an atom 
of any other binary compound. 

237. Causes of the efficacy of the Battery. — As 
no electricity can pass in the voltaic circuit, except 
what is due to electrolytic action, it follows that the 
quantity circulated in a battery, is no greater than 
that evolved by the weakest cell of the battery, and 
that this is no more than would be evolved by a 
single pair of similar plates. However powerful the 
other cells may be, all the electricity evolved by them, 
beyond what its own chemical action transmits, is 
arrested by the weaker cell. The superior efficiency 
of the compound battery appears to be owing to an 
increase in the intensity or energy of propulsion, 
and not in the quantity of the electrical current. 

238. Chemical affinity elective. — The chief char- 
acter by which chemical affinity is distinguished 
from other kinds of attraction, is that which procured 
for it one of its earliest names, viz. elective affinity. 

If lime and magnesia be placed in contact with 



DOUBLE ELECTIVE AFFINITY. 125 

chlorohydric acid, the acid will dissolve the lime be- 
fore it acts on the magnesia. So likewise if sulphuric 
acid and a solution of the alkali soda be poured to- 
gether, they will combine and form a compound 
having neither acid nor alkaline properties. If a 
solution of the alkaline earth baryta be now added, 
the sulphuric acid will leave the soda and unite with 
the baryta; this new combination will be precipi- 
tated as a white powder: and we say that the sul- 
phuric acid has a stronger affinity for the baryta than 
for the soda. Trials of this kind determine the sub- 
stances which appear to have the strongest affinities 
for sulphuric acid; and very useful tables of elective 
affinity are thus formed, in which the relative affini- 
ty for the substance at the head of the column, is 
indicated by the order in which the substances are 
enumerated. 

239. Double elective affinity. — If solutions of ace- 
tate of lead and of sulphate of zinc be poured toge- 
ther, two new salts will be formed, sulphate of lead 
and acetate of zinc. The interchange is commonly 
said to be owing to double elective affinity r , as the 
former are said to be cases of simple elective affini- 
ty. In the instance now given, the sulphuric acid 
has a stronger affinity for the oxide of lead than the 
acetic acid has; and it will therefore of itself decom- 
pose the acetate of lead. But there are instances 
of double decomposition in which this is not the 
case. For example, let the affinity of the acid A for 
the alkali C, be represented by 11, and its affinity for 
the alkali D, by 12. If then the affinity of an acid 
B for C, be represented by 8, and for D, by 11, it is 
evident that the combination of A with D, the force 
of which is 12, could not be disturbed either by the 
alkali C, nor by the acid B, the attraction, of which for 
A and for D is each represented by 11. If, however, 
the compound of B with C, the force of which is 8, 
be added to that of A with D, decomposition will 

11* 



1 26 PRINCIPLES OF CHEMISTRY. 

take place ; for the sum of the quiescent affinities, as 
they are termed, which tend to maintain the bodies 
as they are, is 8+12=20; and the sum of the divel- 
lent affinities, or those which tend to separate them 
and form new compounds, is 11+11=22. 

240. It is a consequence of the law of chemical 
equivalency, that in all cases of double decomposi- 
tion, the resulting compounds are exactly neutralized, 
and that no uncombined acid or alkali remains in 
the solution. A few apparent exceptions will be 
explained in the cases where they occur. 

241. It is difficult to ascertain what decomposi- 
tions and combinations take place in mixed solutions, 
where all the compounds that can be formed are 
soluble. Sulphuric acid will separate the last parti- 
cle of boracic acid from its combination with soda, 
although the whole of it remains in solution. And 
yet it seems probable that two soluble salts generally 
co-exist in proportions regulated by their respective 
affinities. 

242. If one of the resulting salts be insoluble, it 
will in every case, be formed. If any one of the 
salts A D, for instance, be less soluble than the other, 
and the solution be evaporated until this salt crystal- 
lize so as to diminish its relative proportion, an ad- 
ditional portion will be formed; and by continuing 
the process all the acid will combine with the alkali 
D. The salts which are obtained by the evapora- 
tion of dilute solutions are therefore not necessarily 
those which it originally contained; for new combi- 
nations will take place, as we pass the point of satu- 
ration of the several salts whose elements thus co- 
exist in the solution. 

243. Change of properties by Combination. — The 
combination of elements that differ much in their 
electrical relations, that is to say, one of which is 
highly negative to the other, is always accompanied 
with so great a change of properties, that the result- 



EXTRICATION OF HEAT AND LIGHT. 127 

ing compound must be placed in a different class 
and be called by a new name. When the elements 
approximate to each other, in their general charac- 
ter and electrical condition, there are many cases in 
which the resulting compound appears merely to 
blend or slightly modify the properties of its ele- 
ments, and to belong to the same class of bodies in 
a philosophical arrangement. Thus the chloride of 
iodine, the iodide of bromine, and the sulphuret of 
phosphorus, are neither acid nor alkaline, but are sup- 
porters of combustion, or combustible like their ele- 
ments. The metals eminently possess this character 
in their combinations with each other; and the com- 
pounds, or alloys, as they are termed, formed by 
their fusion and intermixture, acquire no new gene- 
ric qualities, but possess all the properties of metals. 

244. Extrication of Heat and Light. — The com- 
bination of the simple elements, which differ greatly 
in their electrical relations, is in general accompani- 
ed with the copious extrication of heat and light, 
the source of which is not known. 

The most common instance of this is the combus- 
tion of inflammable bodies in oxygen gas. When a 
portion of the body is raised to the temperature at 
which combination takes place, the heat that is ex- 
tricated is sufficient to raise an additional portion to 
the same temperature, and thus the combination 
goes on until the whole body is consumed. Where 
the combustible is a compound, which is resolved at 
this temperature into gaseous elements, it burns with 
a flame. These results are beautifully shown in the 
burning of a common oil lamp. 

245. In the case of gunpowder, the inflammation 
is propagated so rapidly through the whole mass, 
and the volume of the gaseous products of the com- 
bustion thus suddenly formed is so great, as to ren- 
der that substance one of the most tremendous en- 
gines of destruction known to man. 



128 PRINCIPLES OF CHEMISTRY. 

246. The union of binary compounds with each 
other is seldom accompanied with the extrication of 
much heat or light, and the more complex the body, 
with the greater facility does it in general change 
its combinations. 

247. Force of Chemical Union* — The stability of 
chemical compounds varies exceedingly. The ele- 
ments which are most firmly united are those form- 
ing binary compounds, and differing greatly in their 
electrical conditions. The most intense heat and the 
most powerful re-agents are scarcely able to separate 
the elements of some of the chlorides and oxides. 

248. In general the ease with which decomposi- 
tion takes place, increases with the increase of one 
of the elements. Thus nitric acid is much more 
easily decomposed than the deutoxide of nitrogen; 
and the metallic per-oxides readilyyield up thesecond 
and third atoms of oxygen, while they part with 
difficulty with the first. 

249. Molecular agitation a cause of Decomposi- 
tion. — On the other hand the per chloric acid, which 
contains 7 atoms of oxygen, is decomposed neither 
by hot chlorohydric acid, nor by organic substances; 
while the protoxide of chlorine is one of the most 
unstable compounds in existence, being decomposed 
by the molecular agitation caused by mere expan- 
sion. 

This instability of composition is still more remark- 
able in the fulminating salts of the metals. The 
slight friction of a grain of sand against a single par- 
ticle of fulminating silver, will be sufficient to cause 
a new arrangement of its elements, which instan- 
taneously assume a gaseous form; and the impulse 
thus given is propagated through the whole mass 
with the rapidity of lightning. 

250. In these cases the forces which hold the atoms 
together are so slight, the divellent so nearly balance 
the quiescent affinities, that the chemical equilibrium 



CAUSE OF DECOMPOSITION. 129 

seems to be maintained by the mere vis inertise of the 
particles. Whatever cause disturbs this and sets 
the atoms of a single particle in motion, decomposes 
that particle, motion is communicated to the adjoin- 
ing, and the decomposition is propagated with more 
or less rapidity through the whole mass. 

251. There are cases of combination in which the 
quiescent affinities are so nearly balanced by the 
divellent, that the presence of a second body may 
effect the decomposition of the first, while at the 
same time the molecular agitation, which takes place 
so disturbs the equilibrium of the particles in the 
decomposing body, and the heat generated is so great 
that it also is decomposed. In no other way can 
we understand what takes place when oxide of silver 
is added to deutoxide of hydrogen. The latter is 
rapidly decomposed, oxygen escapes, and water 
and metallic silver remain. 

252. Examples of this law are of constant occur- 
rence. If a dilute solution of a salt of potassa be 
carefully added to one of tartaric acid, and the mix- 
ture remain perfectly quiet, no change takes place. 
But if it be briskly agitated, the motion thus com- 
municated to the particles is sufficient to destroy the 
equilibrium, and produce a new arrangement, and 
crystals of bi-tartrate of potassa are immediately 
formed. These cases somewhat resemble the forced 
equilibrium of the particles of glass in what are 
called Prince Rupert's Drops. These are formed 
by letting drops of melted glass fall into cold water. 
The external particles are at once solidified and their 
contraction forces the still soft and yielding interior 
mass, into a smaller space than the gradual cooling 
of the whole would have allowed it to occupy. It 
is therefore kept in a state of tension, which acts as 
soon as the external force is removed; so that if the 
least fragment be broken from the small end, the 
whole drop is shivered into fragments. 



130 PRINCIPLES OF CHEMISTRY. 

253. Influence of the presence of a third body. — 
There are cases in which an influence not sufficiently- 
understood is exerted by the presence of a third 
body. Zinc slowly decomposes water, and concen- 
trated sulphuric acid does not attack zinc; yet when 
the three are mixed, the water and the zinc are acted 
on with the greatest energy. In this case the sul- 
phuric acid probably acts by dissolving the thin 
film of oxide, which forms on the surface of the zinc, 
and keeps the metal bright, thus promoting the de- 
composition of the water, which is further aided by 
the heat, generated by the chemical action. 

254. Platinum in a state of minute division may 
be immersed in boiling nitric acid, without the slight- 
est chemical action; while its alloy with silver is 
readily dissolved. In this case the silver is oxidated 
by the decomposition of the nitric acid, and the plati- 
num, in the act of being set free from its combina- 
tion with the silver, being in what is called its nas- 
cent state, also combines with oxygen and forms a 
salt with nitric acid. 

255. Many substances which in their ordinary 
state, exhibit feeble traces of affinity for other bodies, 
and which can scarcely be made to unite with them, 
readily enter into combination, when they are pre- 
sented in what is called their nascent state, that is 
to say, when existing combinations are decomposed 
and elements, capable of uniting into new com- 
pounds are disengaged. It is with extreme difficulty 
for instance, and but in small quantities, that nitrogen 
can be directly combined with hydrogen gas. Yet 
ammonia, which is their most stable compound, is 
always copiously formed when animal bodies which 
contain them both are decomposed. 

256. The combination of gases which have an 
affinity for each other, is greatly promoted by the 
presence of certain solids. Oxygen and hydrogen, 
may be kept together in a glass vessel, for an in- 
definite time, without showing any disposition to 



SOLVENT POWER OF FLUIDS. 131 

unite. Yet if a piece of platinum foil be placed 
within the vessel, drops of water will make their 
appearance on the sides, and the two gases will gra- 
dually combine together. This combination takes 
place so rapidly when the platinum is in a finely 
divided state, such as is obtained by precipitation, 
that the metal becomes red hot, and the gases ex- 
plode. By the same agency, the combination of 
many other gases may be effected. Many porous 
bodies, such as powdered glass, pumice stone, char- 
coal, &c, possess this property at the temperature of 
200°, or 300°. 

257. The union in these cases seems to be effected 
by an adhesion of the gaseous particles to the sur- 
face of the solid body, similar to that of certain 
liquids to solids, so that their mutual affinities are 
brought into play. The phenomenon appears to 
confirm the theory of Dalton, that the repulsive force 
of the particles which constitutes a gas, like the co- 
hesive force which constitutes a solid, obtains only 
between homogeneous particles, and that the differ- 
ent gases so far from repelling, are mutually indif- 
ferent to, each other. 

25S. Absorption of gases by Solids. — In other 
cases the adhesion above spoken of causes a copious 
absorption, analogous to liquefaction. Thus a cubic 
inch of charcoal will absorb 90 cubic inches of am- 
moniacal gas, which it gives out again when heated. 
We cannot but conceive the gas in this case, to be 
held adhesively in a liquid state, amidst the pores of 
the charcoal. 

259. Solvent power of Fluids. — The most simple 
instance of the exercise of chemical attraction is 
afforded by the admixture of two fluids, such as 
water and sulphuric acid, or water and alcohol; or 
by the solution of a solid in a fluid, as of sugar in 
water, or camphor in alcohol. 

In some cases of simple mixture of fluids, and of 



132 PRINCIPLES OF CHEMISTRY. 

the solution of solids in fluids, the proportions in 
which they unite appear to be unlimited. Water 
and alcohol, gum and water, and camphor and al- 
cohol, for example, will combine in all proportions. 
There are other cases in which the union takes place 
in all proportions up to a certain limit. One hun- 
dred grains of water, for example, will dissolve any 
quantity of sea-salt which does not exceed forty 
grains. Its solvent power then ceases, and it is said 
to be saturated. The solvent power of a liquid is 
in most cases, though not always, increased by heat. 
Substances which unite in unlimited proportions, or 
in all proportions up to a certain limit, give rise to 
compounds which have this common character, that 
their elements are united by a feeble affinity, and 
preserve, when combined, more or less of the pro- 
perties which they possess in their separate state. 

260. Influence of cohesion. — Solid bodies seldom 
act upon each other, as chemical affinity is exerted 
only at insensible distances, and the particles of solids 
do not come within the sphere of each other's at- 
traction. Fluids oppose no obstacle to the action 
of chemical affinity, and whether a solid is rendered 
liquid by increasing the heat, or by dissolving it in 
some menstruum, it is in this state that chemical 
affinity acts with its whole energy. Bodies which 
do not unite with each other when they are intimate- 
ly mixed in a fluid state, possess little or no affinity 
for each other. 

The fluidity of one of the bodies is often sufficient 
for effecting chemical union, as in the case of sugar, 
or salt, and water. 

261. Influence of Elasticity. — When an elastic 
fluid enters into the composition of a solid or liquid 
body, its elasticity tends to counteract the effect of 
chemical affinity, and the compound will be decom- 
posed by a third body, having actually a weaker 
affinity for the second than its own. 



CHANGE OF FORM. I 



OO 



The volatility of certain substances affords a ready 
method of separating them from their combinations. 
Alcohol and water have an affinity for each other, 
but the former is volatile at a much lower tempera- 
ture than the latter, and may be almost entirely sepa- 
rated from it by heat. 

262. Change of Density. — Two bodies rarely oc- 
cupy, after combination, the space which they took 
up separately. In general, the density of the com- 
pound exceeds the mean density of its elements. 
For example, 100 measures of water and an equal 
quantity of sulphuric acid, or of alcohol, do not oc- 
cupy 200 measures. The alloys of metals generally 
have a greater density than the mean of the simple 
metals of which they are formed. 

This is still more remarkably the case with the 
gases. Many gases combine without undergoing 
any change of volume. But in the greater number 
of cases a very great condensation occurs, and the 
volume of the resulting compound bears a very sim- 
ple ratio to the volume of its elements; this will 
sufficiently appear from the following table, in which 
all the substances are supposed to be in the gaseous 
state. 

Volumes of Elements. Volume of resulting compound. 

100 N+300 H yield 200 ammonia, 

50 0+100 H " 100 water, 

50 0+100 N " 100 protoxide of nitrogen, 

100 S+600 H " 600 sulphohydric acid, 

100 S+600 " 600 sulphurous acid, 

100 Cl+100 H " 200 chlorohydric acid, 

100 1+100 H " 200 iodohydric acid, 

lOOBr+lOOH " 200 bromohydric acid, 

100 0+100 N " 200 deutoxide of nitrogen. 

263. Change of Form. — A change of form fre- 
quently accompanies chemical combination. The 
combination of gases may give rise to solids or 
liquids; solids sometimes become liquid, and liquids 

12 



134 PRINCIPLES OF CHEMISTRY, 

solid. When in consequence of chemical combina- 
tion, solids or liquids suddenly become gases, deto- 
nation takes place; when a gas and a liquid are 
formed, the escape of the former through the latter 
gives rise to effervescence, and when a solid and a 
liquid are formed, the deposition of the former is 
called precipitation. 

All these changes of density and form in chemical 
combination are accompanied with a change of tem- 
perature, the causes of which have been explained 
in the chapter on caloric. 

264. Change of Colour, — Chemical action is often 
accompanied with change of colour, and no law re- 
gulating this change has yet been discovered. For 
example, iodine, the vapour of which has a violet 
colour, forms a red compound with mercury, a yel- 
low compound with lead, and colours starch blue. 

265. Such are the principal laws which govern 
chemical combination. In the chapter on salts, and 
in that on compound radicals, the subject will be re- 
sumed, and the principles which regulate the consti- 
tution of highly complex bodies, will be further 
developed. 

In treating of compound substances it will be con- 
venient first to consider the bi-elementry compounds, 
ranging them into genera, under the heads of their 
electro-negative element. 



CHAPTER III. 

BI-ELEMENTARY COMPOUNDS. 

266. The compounds which are formed by the 
union of two simple elements may be designated as 
binary compounds of the first order. They con- 
tain several very natural groups, such as acids, alka- 
lies, earths, the haloid salts, and alloys. 



BASES. 135 

267. Principles of Classification. — The elements 
themselves, as has been stated, may be arranged ac- 
cording to their electric relations; with oxygen, the 
most highly electro-negative, at one end of the scale, 
and potassium, the most highly electro-positive at the 
other. If such a table could be formed with entire 
accuracy, each element would be electro-negative to 
all below and electro-positive to all above it in the 
scale. 

The binary compounds may be classed in genera 
according to their electro-negative element. The most 
obvious arrangement would be according to their 
sensible properties as acids, alkalies, &c; but as these 
sensible qualities depend upon, and are controlled by 
their electrical relations, the latter must be adopted 
as the higher principle of classification. 

268. Jlcids. — The earliest definition of an acid 
was, that it is a substance of a sour taste, which 
turns vegetable blues red, and forms neutral salts with 
alkalies. Lavoisier added to the definition that it 
must contain oxygen as an element; and the class was 
gradually enlarged by the addition of bodies which 
have a bitter, and even a faintly sweet taste. Fur- 
ther research compelled chemists to admit into the 
class some bodies which contain no oxygen, others 
which do not affect vegetable blues, and others which 
are quite tasteless, until at last the only part of the 
original definition that is retained, is that they neu- 
tralize alkalies ; a definition which is merged in the 
more comprehensive one now given, that they neu- 
tralize electro-positive compounds of the same genus, 
and are the electro-negative element of the com- 
pounds which they form. 

269. Bases. — In the same manner, has the number 
of those bodies which acids are capable of neutral- 
izing, been enlarged. Although chemists have been 
led to the inconvenient retention of the word acid, 
the common use of which is so different from its 
philosophical meaning; they have, by the adoption 



136 PRINCIPLES OF CHEMISTRY. 

of the term base, happily rid themselves of the like 
inconvenience in speaking of those bodies with which 
acids combine. The term base, is used to express 
all those electro positive compounds which are capa- 
ble of combining with electro-negative ones, (gene- 
rally of the same genus) and which, in so combining, 
acquire new generic properties. This extension of 
the meaning of the term base, has given a correspond- 
ing extension to the antagonist term acid. 

270. The Haloid Salts. — The term salt, like the 
term acid, carried with it into philosophy its popular 
meaning, and here also it has been found necessary 
to extend its meaning, so as to admit substances 
which possess no sensible saline properties. Re- 
stricted, originally, as was believed, to the combina- 
tion of an acid with an alkali, it has been found that 
the most eminently saline of the whole class, contain 
neither acid nor alkali, but are direct binary com- 
pounds of metals with certain electro negative ele- 
ments. 

This group of salts is called, by Berzelius, the 
Haloid Salts, and consists of the metallic compounds 
of the Salt-Radicals — Chlorine, Iodine, Bromine, 
and Fluorine. 

271. The bi-elementary compounds will here be 
classed under the following heads; viz: Oxides, 
Chlorides, Iodides, Bromides, Fluorides, Sulphurets, 
Phosphurets, Carburets, and Alloys. 



Section I. 



THE OXIDES. 

272. The oxides form several well defined groups. 
The non-metallic elements, are all placed at the 
negative end of the scale, and their oxides are, with 



THE OXIDES. 137 

the exception of a few protoxides, the electro nega- 
tive elements of a series of secondary compounds, 
and constitute the most numerous class of acids. 
The non metallic protoxides, which are not acids, 
do not appear to act the part of bases. If we regard 
hydrogen as a gaseous metal, which its chemical 
relations authorize us to do, there will be no excep- 
tion to this rule. 

Fluorine is the only element which has not yet 
been combined with oxygen. 

273. Oxygen forms, with the metals at the posi- 
tive extremity of the scale, a series of protoxides, 
having well marked characters. The protoxides of 
potassium, sodium, and lithium, are alkalies; those 
of barium, strontium, calcium, and magnesium, alka- 
line earths. 

These protoxides are all powerful electro positive 
bases. The alkalies are distinguished by their great 
solubility in water, by a peculiar acrid taste, by 
turning vegetable blues green, and vegetable yellows 
brown, and by forming compounds soluble in water 
with oils. The alkaline earths have these properties 
in a less degree; baryta being the most, and mag- 
nesia the least alkaline of the series. A few of these 
metals form deutoxides and teroxides, which do not 
appear to possess either basic or acid properties. 

The metals which rank next below these in the 
scale, are the bases of the earths, giucina, yttria, tho- 
rina, alumina, and zirconia; their oxides are char- 
acterized by tastelessness, insolubility, and difficult 
fusibility. But one oxide of each of these metals is 
known. 

The highly basic properties of water, place it near 
the group of alkalies and alkaline earths, to the per- 
oxides of which, the peroxide of hydrogen has also 
much analogy. 

274. With most of the remaining metals, oxygen 
forms several oxides, of which the lower degrees of 

12* 



138 PRINCIPLES OF CHEMISTRY. 

oxidation are more or less basic, and the higher 
degrees are either indifferent to acids and to bases 
as the deutoxide of lead, or acid as the teroxides of 
chrome and manganese. The tendency to form acids 
with oxygen, is greatest in those metals which are 
nearest the electro negative end of the scale. 

It will be most convenient to arrange the oxides 
into sub orders, corresponding with the above dis- 
tinctions. 

Sub-order First. 

WON METALLIC OXIDES. 
OXIDES OF CHLORINE. 

275. Protoxide of Chlorine, Hypochlorous Jlcid. 
CI 0. 35.42+8=43.42. This acid is prepared by the 
agitation of finely powdered deutoxide of mercury 
with water in a bottle of chlorine gas. The gas is 
absorbed by the peroxide, a portion of which it de- 
composes. One portion of the chlorine unites with 
the mercury, and another with the oxygen that has 
been set free, forming hypochlorous acid, which is 
dissolved by the water. Pure hypochlorous acid is 
a gas of a pale yellow colour. Its concentrated so- 
lution has a strong acrid, but not sour taste; and its 
odour is penetrating, somewhat resembling that of 
chlorine. It bleaches like chlorine, and destroys the 
epidermis like nitric acid. It is one of the most 
unstable compounds known. Its concentrated solu- 
tion spontaneously decomposes, and the gas explodes 
with a flash of light when the temperature is slightly 
raised. Two volumes expand into three, of which 
one is oxygen, and two are chlorine. The hypochlo- 
rous acid combines with bases to form salts, which 
are remarkable for their bleaching properties. 

276. Peroxide of Chlorine. Chlorous Acid. — - 
ClO^; 35.42+32=67.42. This acid is prepared by 
carefully adding dilute sulphuric acid to chlorate of 



CHLORIC ACID. 139 

potassa. The chloric acid, in being disengaged from 
the potassa, is itself decomposed, and every three 
atoms which are set free, form two of chlorous, and 
one of per chloric acid. 

Chlorous acid is a gas, of a bright yellowish green 
colour, and an aromatic odour; it is rapidly absorbed 
by water, it has no action on mercury, it does not 
combine with the alkalies, and it destroys most 
vegetable colours. Phosphorus takes fire in this 
gas, causing an explosion; it explodes violently 
when heated to 212°, emitting a strong light. Forty 
measures occupy after explosion the space of 60 
measures, of which 20 are chlorine and 40 oxygen, 
so that it is composed of 100 measures of chlorine 
and 200 of oxygen, condensed into 200 measures; 
its specific gravity is therefore 2.3374. 

Chlorous acid gas is condensed by pressure into 
a yellow liquid. It forms salts with alkalies, which 
are speedily decomposed into chlorates and chlorides. 

277. Chloric rfcid.—Ci 5 ; 35.42+40=75.42. 
This acid may be obtained in solution, by the careful 
decomposition of a dilute solution of chlorate of ba- 
ryta by sulphuric acid. It reddens vegetable blue 
colours, has a sour taste, and forms neutral salts 
called chlorates. It may be distinguished from chlo- 
rine by being destitute of bleaching properties, and 
from chlorohydric acid by not occasioning a precipi- 
tate in a solution of nitrate of silver. The solution 
of chloric acid may be concentrated by a gentle heat, 
until it acquires an oily consistence, when it has a 
yellowish tint, and the odour of nitric acid, and sets 
fire to paper and other dry organic matter. Chloric 
acid may be known by its property of forming with 
potassa a salt of a pearly lustre, which crystalizes in 
tables, and deflagrates on burning charcoal like nitre. 

Chloric acid closely resembles nitric acid in its 
properties. It has never been obtained in an isolated 
form, being incapable of existing except in combi- 
nation with water or a base. 



140 PRINCIPLES OF CHEMISTRY. 

27S. Per Chloric Acid.— C10 7 ; 35.42+56=91.42. 
This acid is prepared from the perchlorate of po- 
tassa, by mixing it with half its weight of sulphu- 
ric acid, and heating the mixture; white vapours 
arise which condense in the receiver into a colour- 
less liquid. Its concentrated solution has the specific 
gravity of 1.65, fumes lightly in the air, and boils at 
392°. By distillation with sulphuric acid, in order to 
separate the superfluous water, a solid hydrate may 
be obtained in prismatic crystals. Like the chloric 
acid, it exists only in combination with water or other 
bases. It is the most stable of the oxides of Chlo- 
rine. It does not possess bleaching properties, and is 
one of the most powerful re-agents among the acids. 

OXIDES OF IODINE. 

279. Iodic Acid.— -10 ? ; 126.3+40=166.3. This 
acid is formed when iodine is brought into contact 
with protoxide of chlorine. It is a white semi-trans- 
parent solid, with a strong astringent, sour taste, and 
no odour. Its density has not been ascertained, but 
it sinks rapidly in sulphuric acid. It fuses and is 
decomposed at 500° F. It detonates when mixed 
with inflammable organic substances, is deliquescent 
and very soluble in water, and forms salts which 
deflagrate like nitre. 

280. Periodic Acid.— I T ; 126.3+56=182.3. This 
acid is analogous in its composition to per-chloric 
acid, though little is known of its properties. 

OXIDES OF BROMINE. 

281. Bromic Acid.— Br 5 ; 78.4+40=1 18.4. Bro- 
mic acid closely resembles chloric acid. Its solution 
cannot be concentrated beyond a certain point with- 
out undergoing decomposition. It is the only known 
oxide of bromine. 

OXIDES OF SULPHUR. 

282. Sulphurous Acid.—§0 2 ; 16.1+16=32.1. 
Sulphurous acid is the sole product of the com- 



SULPHURIC ACID. 



141 



bustion of sulphur in dry oxygen gas. The best 
method of obtaining it is by the action of sulphuric 
acid on mercury. When two parts of mercury and 
three of sulphuric acid are gently heated in a glass 
retort, the mercury is oxidated at the expense of a 
part of the sulphuric acid which is converted into sul- 
phurous acid gas, that must be collected over mer- 
cury. 

At the usual pressure and temperature sulphurous 
acid is a permanent gas, of the specific gravity of 
2.2117, and of a suffocating, pungent odour; it ex- 
tinguishes burning bodies without being itself in- 
flammable, and is fatal to animal life. 

Water dissolves 33 times its volume of this gas, 
and acquires its peculiar odour. The gas may be 
expelled unchanged by heat, but it is gradually con- 
verted into sulphuric acid by the absorption of oxy- 
gen from the water. Sulphurous acid bleaches most 
vegetable colours, without decomposing the colour- 
ing principle, for the colour may be restored by an 
alkali or stronger acid. It absorbs oxygen from 
water, nitric acid, and many other substances, and is 
converted into sulphuric acid; and it is, on the other 
hand, produced by the de-oxidation of sulphuric 
acid. It may be passed through red hot tubes with- 
out change, but is decomposed at a red heat by 
hydrogen, carbon, and potassium. Sulphurous acid 
liquefies under a pressure of two atmospheres. The 
liquid acid has a specific gravity of 1.45, and boils at 
14° F. 

2S3. Sulphuric J3cid.— SO 3 ; 16.1+24=40.1. Sul- 
phuric acid is a tough, elastic, white crystalline solid; 
which liquefies at 66° F., and boils at 104° to 122°, 
forming, when there is no water present, a trans- 
parent vapour. This anhydrous acid has a powerful 
affinity for water; it emits dense white fumes in a 
moist air, and unites with an atom of water, forming 
the well known oil of vitriol, which is a liquid sul- 



142 



PRINCIPLES OF CHEMISTRY. 



phuric acid, composed in its most concentrated state, 
of 1 sulphuric acid 40.1+1 water 9z=49.1. When the 
vapour of this anhydrous acid is brought into con- 
tact with the dry alkaline earths, they combine with 
brilliant incandescence, and form the sulphates of 
these earths. 

284. The sulphuric acid of commerce is prepared 
in two ways. The first is by decomposing the pro- 
tosulphate of iron by heat. The salt is dried until it 
loses all its water of crystallization, and is then ex- 
posed in proper vessels to a red heat, which expels 
all its acid. This is the process pursued at Nord- 
hausen in Germany, and the acid thus prepared is a 
dense, oily, brownish liquid, of the specific gravity 
of 1.9, which emits copious white fumes, and is 
known by the name of fuming sulphuric acid. By 
careful distillation, in a retort connected with a re- 
ceiver surrounded by snow, a transparent vapour 
passes over and condenses into the tough crystalline 
mass already mentioned as anhydrous sulphuric 
acid. The liquid remaining in the retort is common 
oil of vitriol, so that the Nordhausen acid is a com- 
pound of the two, consisting, according to Dr. Thom- 
son, of one atom of anhydrous, and one of hydrated 
acid. 

285. The usual method of manufacturing oil of 
vitriol, is by the combustion of a mixture of eight 
parts of sulphur and one of nitrate of potassa. This 
is burnt in a furnace so contrived that the current of 
air which supports the combustion carries the pro- 
ducts into a large leaden chamber, the bottom of 
which is covered to the depth of several inches with 
water. The nitric acid of the nitrate is decomposed, 
by the heat of the burning sulphur, into oxygen and 
deutoxide of nitrogen. The former supports the 
combustion, and the latter, uniting with the oxygen 
of the atmosphere, is converted into nitrous acid, 
and carried along with the sulphurous acid, into the 



SULPHURIC ACID. 143 

chamber. They here combine with the vapour of 
water into a crystalline compound, which is deposit- 
ed on the walls of the chamber and in the water. 
By contact with water this crystalline compound is 
converted into sulphuric acid and deutoxide of nitro- 
gen, the latter of which is reconverted into nitrous 
acid by the oxygen of the atmospheric air in the 
chamber, and combines with the sulphurous acid 
and vapour into the same crystalline compound, 
again to be decomposed into sulphuric acid and 
deutoxide. In this manner the whole of the sul- 
phurous acid is converted into sulphuric. When the 
water in the chamber is sufficiently charged with 
acid it is drawn off and concentrated by boiling in 
leaden and glass vessels, until it has gained the 
density requisite for strong oil of vitriol. 

286. Hydrated sulphuric acid, or oil of vitriol, is 
a dense, colourless, oily fluid, which boils at 620° F., 
has a specific gravity varying from 1.847 to 1.85. It 
is one of the strongest of the acids, separating all the 
others more or less completely from their combina- 
tions with the alkalies. It decomposes all vegetable 
and animal substances by the aid of heat. It has a 
strong acid taste, and reddens litmus paper even 
when very much diluted. 

Sulphuric acid has a powerful affinity for water, 
extricating much heat during the combination, and 
forming several definite hydrates with it. When a 
dilute acid is evaporated at 400°, it acquires a spe- 
cific gravity of 1.78, and becomes a hydrate contain- 
ing two atoms of water, which solidifies at 32°, 
forming large regular crystals that, remain solid at 
45°. By evaporating a still more dilute acid at 212° 
in vacuo, a third hydrate is formed, having a specific 
gravity of 1.632, and containing three atoms of wa- 
ter. These hydrates appear to form distinct classes 
of salts. 

287. When the vapour of sulphuric acid is passed 



144 PRINCIPLES OF CHEMISTRY. 

through a red hot porcelain tube, it is decomposed 
into two volumes of sulphurous acid, and one volume 
of oxygen. 

288. There are two other acids of sulphur; the 
hyposulphurous S 2 2 ; 32.2+16=48.2, and the hy- 
posulphuric S 2 5 ; 32.2+40=72.2. The former 
is a very unstable compound, and is remarkable for 
forming with silver a salt of an intensely sweet, with- 
out any metallic taste. 

2S9. There is solid ground for believing that sul- 
phurous acid is the only one of the above oxides that 
is a direct compound of sulphur and oxygen, and 
that it is the base of all the others. It is the only 
one which can be directly prepared from its elements, 
and it is always evolved in the decomposition of the 
others. On this view the sulphur in sulphurous acid 
is fully saturated with oxygen, and cannot unite 
with anymore; but the acid itself acts as a com- 
pound radical, and combines with simple and 
compound bodies. It does not unite directly with 
oxygen, but it does so with nitrous acid, and the 
compound is decomposed by water, and produces 
sulphuric acid S0 2 +0 as detailed above. It com- 
bines with sulphur to form hyposulphurous acid 
S0 2 +S, which is a true sulphur acid. Two atoms 
combine with oxygen to form hyposulphuric acid 
S 2 4 +0. It also combines with chlorine to form 
chloro sulphurous acid S0 2 +CL, with iodine to form 
iodo sulphurous acid S0 2 +L, and with nitric oxide 
to form nitro sulphurous acid S0 2 +N0 2 (Kane). 

OXIDES OF SELENIUM. 

290. Oxide of Selenium. — SeO; 39.6+8=47.6. 
Oxide of selenium is a colourless gas, which emits a 
peculiar and powerful odour, resembling decayed 
horseradish. 

291. Selenious Jlcid f — SeO 2 ; 39.6+16=55.6. Se- 
lenious acid may be obtained as a hydrate in pris- 



PHOSPHORIC ACID. 



145 



matic crystals. It has the odour of chlorine, is very 
soluble, and is a powerful acid. 

292. Selenic Acid.— Se0 3 ; 39.6+24=63.6. The 
most concentrated form in which selenic acid has 
been obtained, is that of a liquid hydrate, containing 
an atom of water. Its specific gravity is 2.6, its boil- 
ing point 536°, and it is decomposed if further con- 
centrated. It is a powerful acid, and when heated 
oxidizes gold, but not platinum. Its compounds with 
the bases so closely resemble the corresponding sul- 
phates in colour, crystalline form, and external cha- 
racters, that they are only to be known by being 
decomposed by chlorohydric acid, and detonating on 
ignited charcoal. 

OXIDES OF PHOSPHORUS. 

293. Oxide of Phosphorus.— P ? 0; 47.1+8=55.1. 
Oxide of phosphorus is a solid of a red colour, in- 
soluble, tasteless, and inodorous; permanent in the 
air at 662° F., but taking fire at a low red heat. 

294. Phosphorous Acid.— P 2 3 ; 31.4+24=55.4. 
This acid may be prepared by subliming phosphorus 
through bichloride of mercury in a glass tube. A 
limpid liquid is formed, which is a chloride of phos- 
phorus, and which is converted into phosphorous and 
chlorohydric acids by the action of water. Phos- 
phorous acid has a sour taste, and a smell somewhat 
resembling that of garlic. It has a powerful affinity 
for oxygen, and precipitates several of the metals 
from their salts in a metallic form. When anhy- 
drous it takes fire upon being heated in the open air. 

295. Phosphoric rfcid.—P 2 5 ; 31.4+40=71.4. 
This acid may be prepared by oxidating phosphorus 
by means of nitric acid, and by decomposing the bi- 
phosphate of lime by means of ammonia. 

Phosphoric acid is colourless; it reddens litmus 
paper and neutralizes alkalies ; it is intensely sour 
to the taste, but does not destroy the texture of the 

13 



146 PRINCIPLES OP CHEMISTRY. 

skin like sulphuric and nitric acids. When evapo- 
rated at 300° it becomes a dark thick liquid, like trea- 
cle, and consists of one atom of phosphoric acid and 
three atoms of water. This hydrate has been ob- 
tained in thin crystalline plates by careful evapora- 
tion in vacuo. 

When this terhydrated phosphoric acid is heated 
to 415° it parts with one atom of water. When 
heated to a red heat it parts with two atoms, and 
hardens in cooling into a brittle, transparent solid, 
known by the name of glacial phosphoric acid, 
which is highly deliquescent, and can only be pre- 
served in carefully closed glass or stone bottles. An 
anhydrous phosphoric acid is formed when phos- 
phorus is burnt in dry oxygen gas. 

The water, combined with phosphoric acid, ap- 
pears to form with it three distinct chemical com- 
pounds, possessed of distinct and peculiar properties. 
The anhydrous and the glacial acid appear to be 
identical in their chemical relations, and form salts 
containing one atom of base and one of acid. They 
have been called metaphosphoric acid. The bi- 
hydrated phosphoric acid is distinguished by its pro- 
perty of forming di-salts, containing an atom of acid 
and two atoms of base. In those cases in which it 
unites with a single atom of base, an additional atom 
of water appears to be an essential element of the 
salt. This modification of the acid has received the 
name of pyrophosphoric acid. The ordinary phos- 
phoric acid has a strong tendency to form salts con- 
taining three atoms of base, whether those atoms be 
altogether alkaline, or part alkali and part basic 
water. The salts formed by these modifications of 
phosphoric acid with the same base are likewise of 
modified characters, and have been regarded as 
striking instances of the law of isomerism. 

There is another oxide of phosphorus, the hypo- 
phosphorous acid, which consists of two atoms of 
phosphorus, 31.4, and one of oxygen, 8=39.4. 



ATMOSPHERIC AIR. 147 



OXIDES OF NITROGEN. 

296. Atmospheric Air, — Although atmospheric 
air is not to be regarded as a chemical union of its 
elements, it belongs under this head. 

The atmosphere is a mixture of 23 parts by weight, 
or 208 in volume, of oxygen, with 77 parts by weight, 
or 792 in volume, of nitrogen. They are not, there- 
fore, combined in the ratio of an even multiple of 
their atomic numbers, which is the distinction be- 
tween a mechanical mixture and a true combina- 
tion. The atmosphere possesses all the characters 
of a mere mechanical mixture. There is no change 
in the form, bulk, or other qualities of its elements. 
All the bodies which have an affinity for oxygen 
attract it as easily from the air as if the nitrogen 
were not present. A mixture of the two gases in 
the same proportions has the same density and re- 
fractive power, and agrees in all respects with at- 
mospheric air. 

297. If a thin globe of the capacity of 100 cubic 
inches, provided with a proper stopcock, be weighed, 
and then carefully exhausted of its air by an air 
pump,it will be found that it has lost 31.0117 grains, 
when the thermometer stands at 60° F., (154° C.,) 
and the barometer at 30 inches. One hundred cu- 
bic inches of water, at the same temperature and 
pressure, weigh 25245.8 grains. The atmosphere 
at the earth's surface is, therefore, 815 times lighter 
than water. It is also nearly 11065 times lighter 
than mercury. 

298. The weight of the air is adopted as the stand- 
ard with which the weight of all other aeriform fluids 
is compared. Its specific gravity is, therefore, as- 
sumed to be unity. 

If a glass tube 32 or 33 inches long be filled with 
mercury, and then inverted in a vessel of mercury, 



148 



PRINCIPLES OF CHEMISTRY. 



it will be found that a column of the fluid metal, 30 
inches high, will be sustained in the tube by the 
pressure of the atmosphere on the surface of the 
mercury in the vessel. 

The weight of a column of mercury one inch 
square, and 30 inches high, is nearly 15 pounds, 
which is, therefore, the pressure of the atmosphere 
at the earth's surface; but, as it presses equally in 
all directions, it is not felt by us. The weight of 
this column of mercury being a counterpoise to the 
weight of the atmospheric column, it follows that 
the height of an atmosphere of the same density 
throughout as at the surface would be 30 inches 
XI 1065, or 5i miles. 

299. But as, in consequence of its elasticity, the 
density of the air decreases as we ascend, the actual 
height of the atmosphere is supposed to be about 45 
miles. The elastic force which separates the par- 
ticles becomes at last so feeble as to be no more 
than equal to the attraction of gravitation; and this 
equality limits the further separation of the particles, 
and determines the height of the atmosphere. 

300. In virtue of the law of elastic fluids, that the 
density is directly as the pressure, a volume of air 
which, under a pressure of one pound, occupies 100 
cubic inches, will be compressed into half the space 
by double the pressure, and expand into twice the 
volume under half the pressure; and it is a conse- 
quence of this law and of the law of gravity, that 
the density of the atmosphere decreases in a geo- 
metrical ratio when the height increases in an arith- 
metical one. It has been found by experiments 
made on the Puy de Dome — a mountain in Au- 
vergne in France — that the barometer in ascending 
a height of 3000 feet falls from 28 to 24.7 inches. 
The twelfth term in a decreasing geometrical series, 
having the ratio 28 to 24.7, is 7.038, or nearly 7 
inches. At the height of 3000X12=36000 feet, or 



ATMOSPHERIC AlH. 149 

nearly 7 miles, the density of the air is therefore one 
fourth that of the surface, and the following table is 
founded on this calculation. 

Altitude in miles. Corresponding density. 

1 

7 1 

14 ~\ 

21 e\ 

28 lit 

35 TCT24 

42 1 

^* 4096 

49 1 

^ y T6T84 

301. As the radiant heat of the sun passes through 
the air without any absorption, and does not there- 
fore heat it, the atmosphere must receive its heat 
from contact with the earth. 

The decreasing density of the atmosphere being 
a necessary consequence of its constitution as an 
elastic fluid; and also its capacity for heat being, as 
has been stated in the chapter on caloric, increased 
by rarefaction, and the earth being the source of that 
heat, it follows that the sensible heat of the atmos- 
phere must decrease as the latent or specific heat 
increases; that is, in proportion to the height above 
the earth. For if we forcibly expand a stratum of 
air at any distance from the surface, it will rise until 
it reaches an equally rarefied stratum; its specific 
heat being increased, a sufficient portion of the sen- 
sible heat will be necessarily absorbed to supply it, 
and the temperature will fall. So, on the other 
hand, if a portion be forcibly condensed, it will sink 
until it gain its proper level; the specific heat being 
lessened, all the caloric thus disengaged will become 
free, and raise the temperature. It has accordingly 
been found that in ascending into the atmosphere 
the temperature falls one degree of Fahrenheit for 
about every 352 feet of height. There is conse- 

13* 



150 PRINCIPLES OP CHEMISTRY. 

quently in every latitude a point at which the ther- 
mometer never rises above 32°, or where ice does 
not melt. This point is called the point of perpetual 
congelation, and the line drawn through all these 
points, the line of perpetual congelation. 

The following table shows the height of this point 
in different latitudes. 



Lat. 


Feet. 


Lat. 


Feet. 





15.207 


50 


6.334 


10 


14.764 


60 


3.818 


20 


13.478 


70 


1.778 


30 


11.484 


80 


.457 


40 


9.001 


85 


.117 



302. The atmosphere contains from 4 to 6-10,- 
OOOths of carbonic acid; a minute quantity of light 
carburetted hydrogen gas, and a variable quantity 
of aqueous vapour. The carbonic acid is greater in 
summer than in winter, and by night than by day. 

303. The analysis of atmospheric air, is readily 
performed, in several ways. Phosphorus undergoes 
a slow combustion, at ordinary temperatures, and 
will abstract all the oxygen from a vessel of air in 
about thirty hours. Thin filings or shavings of lead 
rapidly combine with oxygen, and entirely remove 
it from the air. Oxygen combines with twice its 
volume of hydrogen to form water. When, there- 
fore, a mixture of equal measures of atmospheric 
air and hydrogen, contained in a strong and gradu- 
ated glass tube, is exploded by means of the electric 
spark, one third of the diminution in the volume is 
due to oxygen gas. The deutoxide of nitrogen also 
furnishes a ready means of analysis which will be 
noticed when treating of that substance. 

304. The art of determining the purity of the air 
by these and other means, is called Eudiometry, 
and the instruments for ascertaining it Eudiometers, 
or measurers of pure air. After repeated experi- 



PROTOXIDE OF NITROGEN. 151 

ments in every variety of situation, it is fully ascer- 
tained that the proportions of the two gases do not 
sensibly vary on the top of the highest mountains, 
in the deepest forests, in the midst of the most crowd- 
ed cities, over the ocean, and in the open verdant 
plains. 

305. As respiration, combustion, and a great va- 
riety of other processes, are continually consuming 
the oxygen of the atmosphere, there must be some 
source of supply commensurate with these drains. 
This exists in the vegetable kingdom. Plants during 
the day absorb carbonic acid from the air, and evolve 
its oxygen ; the carbon constituting their food. Du- 
ring night this process is reversed ; but it has been 
ascertained that in the whole twenty-four hours they 
give out more oxygen than they absorb, and thus 
probably repair the continual waste from other 
causes. 

306. Protoxide of Nitrogen. Nitrous Oxide, 
NO; 14.15+8=22.15. This gas is prepared by 
heating the nitrate of ammonia in a retort to 400° or 
500° F.,at which temperature it fuses, and is rapidly 
decomposed. The following formula will explain 
the nature of the change which takes place. 

Nitrate of ammonia consists of 

1, nitric acid=l nitrogen 14.15+5 oxygenz=40=:54*15 
1, ammoniazzl nitrogen 14.15+3 hydrogen=3zzl7.15 

71.30 

When this salt is decomposed, the 3 atoms of hy- 
drogen combine with 3 atoms of oxygen and form 
3 atoms of water, while the remaining 2 atoms of 
oxygen combine with the 2 atoms of nitrogen and 
form 2 atoms of protoxide of nitrogen. It thus ap- 
pears that 71.3 grains of nitrate of ammonia will 
yield 44.3 grains of the protoxide. 

307. Protoxide of nitrogen is a colourless gas 



152 PRINCIPLES OF CHEMISTRY. 

which does not affect vegetable blues. Water dis- 
solves its own bulk of it, acquires a sweet taste, and 
a faint, agreeable odour; but gives out the gas un- 
changed at 212°. 

Many substances, when previously kindled, burn 
in this gas with great splendour. Iron wire, char- 
coal, phosphorus, and sulphur, when kindled, burn 
with as much splendour as in oxygen gas, and the 
glowing wick of a taper is immediately rekindled. 
It may be decomposed by a succession of electrical 
sparks, or by passing it through a red hot tube of 
porcelain. It is in both cases resolved into oxygen, 
nitrogen, and nitrous acid. When 100 measures of 
the protoxide and 100 of hydrogen are detonated 
together, both gases disappear, water is formed, and 
100 measures of nitrogen gas remain. As the 100 
measures of hydrogen combine with 50 measures of 
oxygen to form water, it is evident that 100 mea- 
sures of protoxide consist of 100 nitrogen and 50 
oxygen condensed into 100. Its specific gravity is 
thus easily determined to be 1.5239; for 

100 cubic inches of nitrogen weigh 30. 1650 grs. 

50 do. oxygen 17.0936 



100 do. protoxide of nitrogen 47.2586 

308. Protoxide of nitrogen will support respira- 
tion for a short time, not exceeding 3 or 4 minutes, 
and produces a temporary delirium, generally ac- 
companied by the most agreeable feelings of excite- 
ment, which soon, however, subside. From four 
to nine quarts are breathed from a silk bag, and a 
few deep inspirations will be followed by feelings 
resembling those of the earlier stages of intoxication. 
These effects are not uniform, and they are occasion- 
ally of an unpleasant and alarming nature. 

Under a pressure of 50 atmospheres the protoxide 
is condensed into a transparent liquid. 






DEUTOXIDE OF NITROGEN. 153 

309. Deutoxide of Nitrogen. Binoxide of Nitro- 
gen. Nitric Oxide.— NO 2 ; 14.15+16=30.15. The 
best method of preparing this gas, is by the action of 
nitric acid of the specific gravity of 1.2 on copper 
turnings. The nitric acid parts with three atoms of 
its oxygen to the copper, and an atom of nitric oxide 
gas escapes. Three atoms of protoxide of copper 
are formed, which unite with three atoms of the 
remaining nitric acid to form the nitrate of copper. 

310. The deutoxide is a colourless irrespirable gas, 
which excites strong and dangerous spasms in the 
glottis. 

Very few inflammable substances burn in this 
gas; burning sulphur and a lighted taper are ex- 
tinguished by it, but charcoal and phosphorus, if 
immersed when in vivid combustion, burn with in- 
creased brilliancy. With an equal bulk of hydro- 
gen it forms a mixture which burns quietly with a 
greenish-white flame. 

The deutoxide of nitrogen is partially decomposed 
by a succession of electrical sparks, and by passing 
through red-hot tubes. If potassium is heated in 
100 measures of this gas, it is converted into potassa, 
the volume of the gas is reduced one half, and pure 
nitrogen is left in the vessel. The quantity of oxy- 
gen that combines with the potassium is 50 mea- 
sures, so that the deutoxide is composed of equal 
volumes of nitrogen and oxygen, which unite with- 
out any change of bulk ; its specific gravity is there- 
fore 1.0375. 

311. Deutoxide of nitrogen is distinguished from 
all other gases, by the formation of red vapours of 
nitrous acid, whenever it comes in contact with oxy- 
gen gas. This property renders it a very convenient 
test of the presence of oxygen, and useful in the 
analysis of atmospheric air. When 100 measures of 
this gas are introduced into a wide vessel containing 
100 measures of atmospheric air, the red fumes are 



154 PKINCIPLES OF CHEMISTRY. 

speedily formed and absorbed by the water, and one 
fourth of the diminution which takes place is oxy- 
gen gas. 

Both the protoxide and the deutoxide of nitrogen 
form compounds of considerable permanence with 
the pure alkalies. 

312. Hyponitrous ^W.-NO 3 ; 14.15+24=38.15. 
This acid may be formed by mixing 400 measures 
of deutoxide of nitrogen with 100 measure of oxy- 
gen, in a glass tube containing a strong solution of 
pure potassa and inverted over mercury. The acid 
which is generated unites with the potassa and forms 
a hyponitrite of potassa. 

The hyponitrous acid is a liquid, colourless at 0° F. 
and green at common temperatures. In open vessels 
it rapidly passes off in orange vapours of the density 
of 1.72. When mixed with water it is decomposed 
into nitric acid and deutoxide of nitrogen. 

313. Nitrous Acid.— NO^; 14.15 + 32 = 46.15. 
When deutoxide of nitrogen is mixed with oxygen, 
red fumes of nitrous acid are always formed. 200 
measures of the deutoxide (100 nitrogen+100 oxy- 
gen) unite with 100 of oxygen and contract into 
100 measures, so that the specific gravity of nitrous 
acid gas is 3.1775. 

Nitrous acid vapour is condensed into a liquid at 
a low temperature, and the acid may be obtained in 
a liquid form by heating carefully dried nitrate of 
lead in an earthen retort to a red heat, and collecting 
the vapours of nitrous acid, which are formed, in a 
vessel surrounded by a freezing mixture. The liquid 
acid is highly pungent and corrosive; its colour at 
common temperatures is orange-red, at 32° is yellow, 
and at 0° it is colourless. Its density is 1.451, and 
its boiling point 82°. Nitrous acid gas is highly irre- 
spirable and excites violent spasms of the glottis. It 
extinguishes burning sulphur, but phosphorus and a 
taper will burn in it with great brilliancy. 



NITRIC ACID. 155 

Nitrous acid readily parts with its oxygen to the 
more oxidizable bases, and is usually converted there- 
by into deutoxide. It is decomposed, and yields 
oxygen and nitrogen gases by being transmitted 
through a red-hot porcelain tube. 

When nitrous acid gas is passed into water 3 it is 
decomposed into nitric acid and the deutoxide, the 
latter of which escapes with effervescence. The so- 
lution first becomes blue, then blueish-green, green, 
yellow, and orange, according to the relative quan- 
tity of nitric or nitrous acids. The more nitric acid 
the solution contains, the greater is the quantity of 
nitrous acid which it will retain without decomposi- 
tion. When nitrous acid gas is heated, its colour 
gradually deepens, until it becomes at last absolutely 
black. 

314. Nitric Acid.— NO 5 \ 14.15+40=54.15. Ni- 
tric acid may be formed by passing a succession of 
electric sparks through a mixture of oxygen and 
nitrogen gases in which moisture is present. It may 
also be formed by slowly adding deutoxide of nitro- 
gen to an excess of oxygen gas over water. It has 
been proved by this means that the acid consists of 
100 volumes of nitrogen and 250 of oxygen. 

Nitric acid cannot exist in an insulated state, and 
the most concentrated form in which it can be ob- 
tained is a combination of two atoms of acid and 
three of water. 

The nitric acid of commerce is usually called aqua 
fortis, and is generally prepared by decomposing the 
nitrate of potassa by sulphuric acid. The presence 
of water is essential to the process, as without it a 
considerable portion of the nitric acid is decomposed; 
for it is driven off from the potassa by the superior 
affinity of the sulphuric acid, and not finding the 
quantity of water which is necessary to its separate 
existence, is resolved into nitrous acid and oxygen. 

315. Nitric acid, in its purest and most concen- 



156 PRINCIPLES OP CHEMISTRY. 

trated form, is a colourless liquid — eminently acid in 
all its properties — of a specific gravity of 1.5 or 1.51, 
and containing 20 per cent of water. It emits dense, 
white, suffocating fumes, and absorbs water from 
the atmosphere. It boils at 248° F., and may be dis- 
tilled without material change. Dilute nitric acid 
may be concentrated by heat till it gains the density 
of 1.42; but if acid of a greater density than this be 
heated, it is weakened. The strongest nitric acid 
freezes at — 50° F., diluted with half its weight of 
water it congeals at — li°F. while the addition of 
a little more water reduces the freezing point to 
— 45° F. 

Nitric acid has a great affinity for water, and heat 
is disengaged when the two are mixed; from this 
affinity for water it liquefies snow with great rapid- 
ity, so that a mixture of 4 parts of concentrated acid, 
and 7 parts of snow, reduces the thermometer from 
+32° to —30° F. 

Nitric acid acts powerfully on all substances 
which have much affinity for oxygen. It oxidates 
nearly all the metals, and acts on tin, copper, and 
mercury, with great violence. It decomposes all 
vegetable and animal substances, and imparts to 
most of them, and particularly to the skin and nails, 
a permanent yellow stain. It acidifies sulphur and 
phosphorus, and when flung on burning charcoal 
greatly increases the brilliancy of the combustion. 

OXIDES OP HYDROGEN. 

316. Water. HO; 1+8=9. — Water is a transpa- 
rent, colourless, inodorous, and tasteless substance, 
which is solid below 32° and fluid at ordinary tem- 
peratures. It refracts light powerfully, and conducts 
heat very slowly. In its fluid state it is an imper- 
fect conductor, and in its solid state a non-conductor 
of electricity. A cubic inch of water at 62° F. and 



WATER. 157 

30 in. B. weighs 252.458 grains, and its weight is 
taken as the standard to which the weight of all 
other bodies except gases is referred. Water is elas- 
tic and compressible, being compressed 51.3 millionths 
of its bulk by a pressure equal to that of the atmos- 
phere. Water absorbs air by exposure to the at- 
mosphere, and the only means of obtaining it abso- 
lutely pure is by distillation. Water, deprived of all 
its air by ebullition, absorbs gases to which it may 
be exposed in various quantities. 

317. If the air separated from rain or snow water 
be examined, it will be found to contain from 32 to 
34.8 per cent, of oxygen gas. Dalton and Henry 
found that 100 cubic inches of water, at the mean 
temperature and pressure, absorb, of 

Sulphohydric acid gas, 100 cubic inches, 
Carbonic acid, 100 * 

defiant gas, 12.5 " 

Oxygen, 3.7 " 

Carbonic oxide, 1.56 " 

Nitrogen, 1.56 " 

Hydrogen, 1.56 " 

318. Water is one of the most useful and power- 
ful agents we possess. It combines directly and in 
unlimited proportions with many bodies, mingling 
withfiuids, and dissolving solids, which may be sepa- 
rated from it by heat with their original properties 
unchanged, and which retain, even in combination 
with it, their peculiar characters unaltered, except 
by dilution. It combines also in a definite ratio with 
many acids, bases, and salts. Thus the slaking of 
lime is occasioned by the union of that earth with 
an equivalent of water. The concentrated oil of 
vitriol of commerce, is a combination of an atom of 
sulphuric acid and an atom of water. Free nitric acid 
cannot exist except in combination with water, and 
the liquid acid is a compound of two atoms of acid 
with three of water. There are no less than three 

14 



158 PRINCIPLES OF CHEMISTRY. 

distinct combinations of phosphoric acid and water, 
giving rise to distinct classes of salts characterized 
by the presence or absence of water as an essential 
element in their composition. These definite com- 
pounds of water have received the name of hydrates, 
a term liable to misconception from its use in con- 
nexion with other terms. The use in all these cases 
of the adjective hydrated would prevent any con- 
fusion with the names of other combinations of hy- 
drogen. 

The important relations of water to heat have 
already been pointed out in treating of caloric. 

319. Deut oxide of Hydrogen. Peroxide of Hy- 
drogen. H0 2 ; 1+16=17. — Peroxide of hydrogen 
was discovered by Thenard in 1818. It may be ob- 
tained by carefully adding to water acidulated with 
chlorohydric acid, a sufficient quantity of the deutox- 
ide of barium to neutralize it. One atom of the 
oxygen of the deutoxide unites with the hydrogen 
of the chlorohydric acid, and the other atom com- 
bines with the water, while the barium and the chlo- 
rine unite to form chloride of barium. By carefully 
adding sulphuric acid, the whole of the barium is 
precipitated in the form of sulphate of baryta, and 
free chlorohydric acid is left in the solution. The 
process is repeated by adding fresh portions of oxide 
and acid until the water will no longer take up oxy- 
gen, and the peroxide is then concentrated by evapo- 
rating in vacuo the water with which it is still di- 
luted. 

Peroxide of hydrogen is a colourless, transparent, 
inodorous liquid, of the specific gravity of 1.452. It 
has a peculiar metallic taste, and occasions a prickling 
sensation both on the tongue and skin: it whitens 
the latter, and at length destroys its texture; it bleach- 
es litmus and turmeric paper; it remains liquid in 
the greatest cold to which it has been exposed, and 
is slowly volatilized in vacuo; at 59° F. it effervesces 



OXIDES OF BORON. 159 

from the escape of oxygen gas, and if heated to 
212° F., detonates from the rapidity of its decompo- 
sition. Dilution with water and a few drops of 
strong acid, render it more permanent; but it is de- 
composed by most of the metals, and by many of 
the metallic oxides; during which the metals that 
have a strong affinity for oxygen are oxidated, while 
gold, silver, mercury, platinum, and its associated 
metals, retain the metallic state. The protoxides of 
many metals are converted by it into peroxides, and 
the peroxides of lead, mercury, gold, platinum, man- 
ganese, and cobalt, decompose the peroxide com- 
pletely and instantaneously, without becoming more 
highly oxidated. So great is the heat evolved by 
the action of these peroxides, that the tube in which 
the experiment is conducted becomes red hot. All 
the metallic oxides which are reduced to a metallic 
state by exposure to a red heat, are also reduced 
when they decompose the peroxide. 

OXIDES OF CARBON. 

320. The constant presence of this element in the 
products of organic life, renders it convenient to defer 
the consideration of all its compounds, until we 
reach the department of organic chemistry. 

OXIDES OF BORON. 

321. Boric Acid. Boracic Acid. B0 3 ; 10.9+ 
24=34.9. — Boric acid is the only known oxide of 
boron. It is held in solution in the hot springs of 
Lipari, and of Tuscany. It also exists in combina- 
tion with oxide of sodium, in the form of borax, a 
salt that is obtained from the waters of certain lakes 
in India. 

Boric acid may be prepared by adding to a solu- 
tion of borax in four times its weight of water, a 



160 PRINCIPLES OF CHEMISTRY, 

sufficient quantity of sulphuric acid to decompose 
the salt. The boric acid is deposited in white, bril- 
liant, unctuous, crystalline, hexahedral scales, which 
may be purified by washing and crystallization. 

Crystallized boric acid is composed of one atom 
of acid 34.9 and 3 atoms of water 27=61.9. It is 
soluble in 25.7 times its weight of water at 60°, and 
in 3 times at 212°. When it is heated in a platinum 
vessel it fuses, the water of crystallization is entirely 
driven off, and the anhydrous acid remains, forming 
a hard, colourless, transparent glass, which bears a 
white heat without subliming. 

The specific gravity of crystallized boric acid is 
1.48; it is soluble in five parts of boiling alcohol, 
and the solution burns with a beautiful green flame. 
It is inodorous, and its taste is cool and bitterish rather 
than acid. It is one of the weakest of the acids, 
and though it reddens litmus paper feebly, and de- 
composes the alkaline carbonates, it turns turmeric 
paper brown, as do the alkalies, and unites as a base 
with the bi-tartrate of patassa. Borax melts read- 
ily, and promotes the fusion of the more refractory 
minerals, on which account it is much used in min- 
eralogy and the arts as a flux. 

OXIDES OF SILICON. 

322. Silicic Acid. Silica.— Si0 3 ; 22.5+24=46.5. 
— This acid, under its usual forms of silica, silicious 
sand, quartz, rock crystal, and flint, is one of the 
principal constituents of the rocky crust of the globe. 
It may be prepared by igniting rock crystals, plung- 
ing them while red-hot into water, and then pul- 
verizing them. 

Pure silicic acid, as thus prepared, is a light, white 
powder, rough and meagre to the touch, tasteless 
and inodorous, and fusible in the flame of the oxy- 
hydrogen blowpipe. 



METALLIC OXIDES. 161 

Solid silicic acid is insoluble in water, but the acid 
in its nascent state is soluble in considerable propor- 
tions, and the solution, when gently evaporated, de- 
posites a bulky, gelatinous precipitate. This precip- 
itate is a hydrated acid, and does not part with all 
its water, until heated to redness. Silicic acid crys- 
tallizes in hexahedral prisms, terminated by six-sided 
pyramids; the primitive form of which is an oblique 
rhomb. Its specific gravity is 2.66. Although sili- 
cic acid has no action on test paper, nor any of the 
sensible properties of an acid, it combines with al- 
kalies and earths, and decomposes the alkaline car- 
bonates; and possesses the properties of an acid in 
all its chemical relations. 

Sub-order Second. 

THE METALLIC OXIDES. 

Group First. 

ELECTRO NEGATIVE OXIDES — ACIDS. 

323. The metallic acids are those of tellurium, 
(Te 2 , Te 3 ,) arsenic, (As 3 , As 5 ,) antimony, 
(Sb 4 , Sb 5 ,j chrome, (Cr 3 .) vanadium, (V0 3 ,) 
osmium, (Os 4 ,) titanium, (Ti 2 ,) gold, (Au 3 ,) 
molybdenum, (M0 3 ,) tungsten, (W0 3 ,) columbium, 
(Ta 3 ,) tin, (Sn 2 ,) and manganese, (Mn 3 , Mn 2 
7 .) 

324. Jirsenious Jlcid. — As 3 , 75.4x24=99.4. 
Arsenious acid is always produced when arsenic is 
heated in the open air. It is usually met with as a 
white powder. It sublimes at 380° without pre- 
viously melting, yielding inodorous vapours, which 
condense into a brittle colourless transparent mass, of 
a vitreous lustre and conchoidal fracture. This glass 
by exposure to the air gradually becomes opaque 
and milk white, a change which diminishes its specific 
gravity and increases its solubility. The transparent 
acid feebly reddens litmus paper, while the opaque 

14* 



162 PRINCIPLES OF CHEMISTRY. 

acid restores the blue to litmus paper previously red- 
dened. Arsenious acid has a slightly sweet taste 
and leaves an acrid sensation on the palate. When 
slowly sublimed, it crystallizes in regular octohe- 
drons: and it has also been obtained in hexagonal 
scales, the primitive form of which is the rhombic 
prism. One hundred parts of boiling water dissolve 
9.6S parts of the transparent, and 11.47 of the opaque 
acid. 

325. Arsenious acid is one of the most virulent of 
poisons, and its detection is an object of great interest 
to the chemist and physician. The most certain me- 
thod is to reduce the acid to the metallic form. This 
is readily done by igniting a mixture of the suspected 
powder with black flux in a glass tube. The me- 
tallic arsenic sublimes as it is formed, and may readily 
be distinguished by the metallic film which forms in 
the tube. 

Arsenious acid forms a perfectly insoluble salt 
with the protoxide of iron, which is therefore, when 
freshly prepared, and taken in sufficient quantity, 
an effectual antidote to its effects. 

326. Manganic Acid. — Mn 3 . Permanganic 
acid, Mn 2 7 . The former of these acids is so 
readily decomposed that it cannot be kept in a free 
state. The concentrated solution of the perman- 
ganic acid has a rich red colour, and is rapidly de- 
composed by contact with organic substances. It 
bleaches colouring matters, and at 86°, is resolved 
into oxygen, and peroxide of manganese. 

These acids are prepared from a salt long known 
under the name of chameleon mineral. It is best 
prepared by finely triturating 7 parts of black oxide 
of manganese with 6 of chlorate of potassa, and 
adding a strong solution of S parts of caustic potassa. 
The mixture is to be dried, powdered, and kept at a 
red heat for one or two hours in a platinum crucible. 
The salt formed is the manganate of potassa, and 






METALLIC OXIDES. 163 

its solution which is of a rich grass green colour, soon 
becomes blue, purple, and red, from the deposition of 
oxide, and the formation of the permanganate of 
potassa. 

327. Chromic acid.— Cr 3 ; 28+24=52. Chro- 
mic acid may be obtained in crimson needles of 
great brilliancy, by placing a slip of moistened paper 
in the vapour of perfluoride of chrome. Pure dry 
chromic acid is black when warm, and of a deep red, 
when cold; it is very soluble in water, has a sour 
taste and strong acid properties. It bleaches vegeta- 
ble and animal colouring matters, parting with oxy- 
gen and being converted into the green oxide. 

328. Osmic acid is formed when osmium is burn- 
ed, and is obtained in long white needles, having a 
pungent acid odour. It is soluble in water, and has 
no action on vegetable colours. 

The remaining acids present nothing of particu- 
lar interest to the student. They are generally col- 
oured, nearly or quite insoluble, and tasteless, and 
some of them are themselves basic to stronger acids. 

Group Second. 

329. This group comprehends the metallic oxides, 
which are neither acids, alkalies, nor earths. 

They are generally coloured, and impart their 
colour by fusion to glass; a very few of them are 
slightly soluble in water; the protoxides are strong 
bases; while many of a higher degree of oxidation, 
show no tendency to combine with either acids or 
alkalies, and others appear to be capable of combin- 
ing with both. As prepared in the laboratory, they 
are mostly in the form of opaque powders; though 
the greater number of them exist in nature in beau- 
tiful crystalline forms. When not tasteless, they 
have a peculiar metallic taste. 

330. This group includes the oxides of antimony, 
Sb0 3 ; tungsten, W0 2 ; molybdenum, MoO, Mo0 2 ; 



164 PRINCIPLES OF CHEMISTRY. 

gold, Au0 2 ; titanium, TiO; platinum, Pt 0,Pt 2 ; 
osmium, 0s0,0s0 2 ; Uranium, UO, U0 3 ; rhodium, 
RO,R 2 3 ; iridium, IrO,Ir 2 3 ; Ir0 2 ,lr0 3 ; Vana- 
dium, VO; chrome, Cr 2 3 ; mercury, HgO, Hg0 2 ; 
palladium,' Pd 2 0, PdO, Pd0 2 ; silver, AgO, Ag 2 ; 
copper, Cu 2 0, CuO, Cu0 2 ; lead, Pb 2 0, PbO, Pb0 2 e ; 
tin, SnO, Sn 2 3 ; bismuth, Bi0 3 ,Bi0 5 ; cobalt, CoO, 
Co 2 3 ; nickel, NiO,Ni 2 3 ; iron,FeO,Fe 2 3 ; man- 
ganese, MnO,Mn 2 3 , Mn0 2 ; cadmium, CdO; zine, 
ZnO; cerium, CeO, Ce 2 3 . 

331. The protoxide of mercury is a black insolu- 
ble powder, prepared by quickly mixing calomel 
(protochloride of mercury) with a solution of potassa. 

The deutoxide of mercury is prepared, either by 
heating mercury in oxygen gas till it is oxidated, or 
by expelling the acid from nitrate of mercury by 
heat. It is the substance called red precipitate. It 
is commonly in the form of red crystalline scales, and 
is slightly soluble in water. The solution has a 
metallic taste, and turns delicate vegetable blues 
green. 

332. The dinoxide of copper is the ruby copper 
ore of mineralogists; it is a reddish brown powder, 
much less acted on by moist air than pure copper, 
and which, therefore protects the surface of the cop- 
per, upon which it has been formed. 

The protoxide of copper may be formed by igni- 
ting the nitrate of copper. It is a dull black powder, 
which is entirely reduced to metallic copper, when 
heated to a dull red heat in contact with carbon, or 
with hydrogen gas. As the quantity of carbonic 
acid, or of water, which is thus formed can be measur- 
ed with great exactness, this oxide is preferred to all 
other reagents in the ultimate analysis of organic 
bodies. 

333. Lead forms three oxides similar in composi- 
tion to those of copper. 

The dinoxide is a dark gray powder; the pro- 



OXIDES OF IRON. 165 

toxide is formed by exposing melted lead to the air 
until a crust of the protoxide collects on the surface; 
the protoxide is of a lemon yellow colour, and is the 
pigment called massicot; when partially fused by 
heat it is called litharge. It is insoluble in water, 
has a specific gravity of 9.4214, parts with its oxy- 
gen to combustible matters, has a foliated texture 
after being fused, and unites readily with earthy sub- 
stances into a transparent glass. 

The peroxide is of a dark brown colour, is insolu- 
ble in water, and converted by a red heat, and by 
strong acids, into protoxide and oxygen gas. 

The mixture in variable proportions of the pro- 
toxide and peroxide of lead,forms the pigment known 
by the name of minium or red lead. Minium is 
formed by exposing lead to the continued action of 
a current of hot air, without allowing it to fuse. It 
has a bright scarlet colour, is much used as a pig- 
ment, and in the manufacture of flint glass. 

The deutoxide of lead is remarkable for forming 
pyrophyri, with the organic acids. A mixture of 
2i parts of perfectly dry tartaric acid, and of 8 parts of 
peroxide, or of 1 of oxalic acid, and 5i of peroxide, 
speedily inflames, and continues a long while at a 
red heat. 

334. There are two distinct oxides of iron, the pro- 
toxide and the sesqui-oxide, or peroxide. The pro- 
toxide exists as a saline base in sulphate of iron, and 
is precipitated as a white hydrate, which is gradu- 
ally converted by exposure to the air into the red 
oxide. 

The peroxide or red oxide of iron is the mineral 
known by the name of red haematite; its hydrate, 
containing two atoms of water, is the mineral called 
brown haematite. 

The peroxide is not magnetic; it tinges glass of a 
red or yellow colour. It is prepared by exposing 
the sulphate to an intense heat, and is known to arti- 



166 PRINCIPLES OF CHEMISTRY. 

sans by the name of colcothar, and crocus martis. 
The native black oxide of iron appears to be a com- 
pound of these oxides in various proportions. 

335. The protoxide of zinc is formed during the 
combustion of zinc: it is a flocculent white powder, 
insoluble in water, fixed in the fire, and a strong 
salifiable base. 

336. The protoxide of tin is prepared by decom- 
posing the chloride, by an alkaline carbonate. The 
precipitate is the hydrated oxide, which must be 
carefully dried at a low temperature. It is a white 
powder which burns like tinder when suddenly heat- 
ed to a red heat. 

The sesqui-oxide of tin is soluble in chlorohydric 
acid, and the solution, on being mixed with a solu- 
tion of chloride of gold, forms a precipitate much used 
in enamel painting, and called the purple powder 
of Cassius. 

Group Third. 

THE EARTHS. 

337. The earths are tasteless, insoluble, white 
oxides, which are strongly basic ; and they are the 
only known oxides of their respective metals. Yttria, 
and thorina, are protoxides, and alumina, glucina, 
and zirconia, sesqui-oxides. With the exception of 
alumina, they are very rare minerals. Thorina is 
the heaviest of all the earths, its specific gravity being 
9.4. Glucina is remarkable for the sweet taste of 
its salts; and zirconia approaches, in many of its 
properties, to silica. 

338. Jllumina. — Al 2 3 ; 27.4+24=51.4. Alu- 
mina is one of the most abundant products in nature, 
constituting, in a greater or less state of purity, the 
different kinds of clay, and being a constituent of 
many rocks. Sapphire, and the ruby, two of the 



THE EARTHS. 167 

most precious and beautiful of gems, are nearly pure 
alumina. 

Alumina may be prepared by decomposing a so- 
lution of sulphate of alumina and potassa, by means 
of an alkali, and repeatedly washing the precipitate 
until all the sulphate of potassa is removed. The 
alumina forms a bulky gelatinous precipitate, which 
becomes a semi-transparent, and afterwards a white, 
friable mass, and can only be deprived of its water by 
exposure to a white heat. It may also be prepared 
by exposing the sulphate of alumina and ammonia 
to a strong heat, by which the acid and alkali are 
driven off. 

Alumina is a tasteless, inodorous, insoluble, white, 
friable solid, which has a powerful affinity for water, 
attracting it from the air, and adhering tenaciously 
to the tongue. It forms with water a soft, cohesive 
mass, capable of assuming any form in the mould or 
the lathe, and retaining it when dry. Alumina is 
capable of uniting both with acids as a base, and with 
bases as an acid. It is separated from acids as a 
hydrate by all the alkaline carbonates, but the pre- 
cipitate is redissolved by an excess of alkali. 

Aluminium forms but one compound with oxygen, 
and we have therefore no direct means of ascertain- 
ing the atomic composition of alumina. It is from 
its close resemblance in its form, and in all its combi- 
nations, to the sesqui-oxide of iron, that chemists 
have inferred that it is a sesqui-oxide. 

339. Alumina is remarkable for its tendency to 
unite with organic matters. If cotton cloth be im- 
mersed in a solution of acetate of alumina, the earth 
will deposite itself completely on the fibres of the 
cloth, and leave the acetic acid free. If the cloth be 
then dipped in a solution of some organic colouring 
matter, this also will unite with the alumina, and 
become fixed upon the cloth as a permanent dye. 



168 PRINCIPLES OF CHEMISTRY. 

Group Fourth. 

THE ALKALINE EARTHS. 

340. The metallic oxides of this group, are more 
or less soluble; they turn vegetables blues green, 
and with the exception of magnesia, they are alka- 
line to the taste ; but they are inferior in all these 
qualities to the alkalies, and they do not form with 
oil compounds soluble in water, nor a transparent 
glass with silex. 

341. Protoxide of Barium, Baryta. — BaO; 68.7 
+8=76.7. Baryta may be prepared by subjecting 
nitrate of baryta to a red heat, and by heating in- 
tensely a mixture of charcoal and the carbonate of 
baryta. 

It is a gray powder, of the sp. gr. of 5. It has a 
sharp caustic alkaline taste, turns vegetable blues 
green, neutralizes the strongest acids, and requires 
a high temperature to fuse it. It is insoluble in al- 
cohol, has a very strong affinity for water, in com- 
bining with which it extricates an intense degree of 
heat, and forms a bulky hydrate, consisting of one 
atom of baryta and three of water. This hydrate is 
soluble in three times its weight of boiling water, and 
crystallizes on cooling in transparent flattened prisms, 
which contain one atom of baryta and twenty of 
water. 

342. Barium also forms a deutoxide, which may 
be prepared by heating four parts of baryta to red- 
ness, in a platinum crucible, and gradually adding 
one part of chlorate of potassa. The deutoxide is 
used in the preparation of the peroxide of hydrogen. 

343. Protoxide of Strontium, Strontia. — Sr 0; 
43.8+8=51.8. Strontia so closely resembles baryta 
in its properties, that they were once supposed to be 
identical. It is prepared in the same manner from 



TROTOXIDE OF MAGNESIUM. 169 

its nitrate and carbonate. Its hydrate contains one 
atom of strontia and nine atoms of water, and is solu- 
ble in boiling water, which deposites on cooling, trans- 
parent crystals, in quadrangular tables, composed of 
one atom of strontia and twelve of water. 

The salts of strontia tinge the flame of alcohol of 
a crimson colour. 

344. Protoxide of Calcium, Lime. — Ca ; 20.5+ 
8— 2S.5. Lime is a brittle, white, earthy solid, of 
the specific gravity of 2.3. It has a strong affinity 
for water, and combines with it into a solid hydrate, 
consisting of an atom of each. Much heat is extri- 
cated during this combination, and the process is 
called slaking. Hydrate of lime parts with its water 
at a red heat; it is soluble in water, and the solution 
has an acrid alkaline taste, and turns vegetable 
blues green. Lime is more soluble in cold than in 
hot water, being soluble in 635 parts of water at 32°, 
in 778 at 60°, and in 1270 at 212°. By careful evapo- 
ration of this solution in vacuo, and absorbing the 
vapour by means of sulphuric acid, lime has been ob- 
tained in transparent hexahedral crystals containing 
an atom of water. Lime is one of the most infusible 
bodies known, melting with difficulty in the flame of 
the oxy-hydrogen blowpipe. When heated to full 
redness it phosphoresces powerfully, a property pos- 
sessed also by the other alkaline earths. 

Lime is prepared by exposing its carbonate to a 
full red heat: it has a strong affinity for carbonic 
acid, with which it forms an insoluble salt, and must 
therefore be carefully kept from the air. The salts 
of lime give to the flame of the blowpipe a dull, 
brownish red colour. 

345. Protoxide of Magnesium, Magnesia. — Mg 
0; 12.7+Sz=20.7. Magnesia is a white, friable pow- 
der, of an earthy appearance, and, when pure, taste- 
less and inodorous. Its specific gravity is 2.3, and 
it is highly infusible. It has a feebler affinity for 

15 



1 70 PRINCIPLES OF CHEMISTRY. 

water than lime, and in its combination with that 
liquid does not extricate heat, but forms, and slowly 
consolidates beneath water into a solid cement like 
plaster of paris. Like lime, magnesia is more soluble 
in cold than in hot water, although it dissolves very 
sparingly in either. It is soluble in 5142 times its 
weight at 60°, and 36,000 times at 212°. The solu- 
tion is too weak to affect vegetable blues, but pure 
magnesia turns litmus paper brown. The hydrate 
of magnesia is found native, and contains an atom 
of each of its elements. Magnesia has a strong 
affinity for carbonic acid, and must therefore be pre- 
served in close vessels. 

Group Fifth. 

THE ALKALIES. 

346. The word kali is the Arabic name of a plant, 
from the ashes of which the alkali, now called soda, 
was obtained. It has been incorporated into the 
languages of Europe, and has passed into a generic 
term, signifying substances of an acrid bitter taste, 
soluble in water, turning vegetable blues green, and 
the yellow of turmeric brown; forming soaps with 
oil, and salts with acids, and having a powerfully 
caustic action on the skin. Three alkalies have long 
been known in the arts, viz. potash, or potassa — the 
vegetable alkali which is obtained from the ashes of 
plants in general; soda, or natron — the mineral 
alkali, which is obtained from the ashes of marine 
plants, and is also found as a saline concretion from 
the waters of certain lakes ; and ammonia, or the 
volatile alkali, which is evolved during the decom- 
position of animal substances. A fourth, named 
Lithia, has in modern times been added to the list. 
The description of ammonia will be deferred to the 
department of Organic Chemistry. 



PROTOXIDE OF LITHIUM. 171 

347. Protoxide of Potassium, Potassa. — KO,39. 
15+8=47.15. Pure potassa can only be prepared 
by exposing thin laminse of potassium to the action 
of dry oxygen gas. It is a white, solid, highly caus- 
tic substance, fusible at a temperature above redness, 
and neither volatilized nor decomposed in the strong- 
est heat to which it has been exposed. It has a 
powerful affinity for water, with which it forms a 
solid hydrate. This hydrate, which was long re- 
garded as the pure alkali, will bear the strongest 
heat without decomposition; it fuses at a heat below 
redness, and assumes a crystalline structure in cool- 
ing. It is soluble in alcohol and in half its weight 
of water, and is much employed in surgery as a 
caustic. The solution of potassa is highly caustic, 
and must be kept in carefully closed vessels, as it 
rapidly absorbs carbonic acid from the atmosphere. 

Hydrate of potassa is prepared by decomposing 
the carbonate of potassa by means of lime. The 
lime forms an insoluble compound with the acid, 
and sets the alkali free. The solution is filtered and 
concentrated rapidly by boiling in a leaden, and at 
the close of the operation, in a silver vessel. 

348. Protoxide of Sodium, Soda. — NaO; 23.3+ 
8=31.3. The protoxide of sodium, soda, or natron, 
is formed by the oxidation of sodium in dry oxygen 
gas. In its anhydrous state it is a gray solid, diffi- 
cult of fusion, and closely resembling potassa. With 
water it forms a solid hydrate, which is very caustic, 
soluble in water and alcohol, and like potassa emi- 
nently alkaline. It is prepared from its carbonate 
in the same manner as potassa. 

The salts of soda are all soluble in water, and 
tinge flame of a yellow colour* 

349. Protoxide of Lithium, Lithia.—!LO 10+S 
=18. Lithia is closely allied to potassa and soda, 
but tinges flame of a red colour, has a greater neu- 
tralizing power, and forms sparingly soluble com- 
pounds with carbonic and phosphoric acids. 



172 PRINCIPLES OF CHEMISTRY. 



Section II. 

THE SULPHURETS. 

350. The compounds, of which sulphur is the elec- 
tro-negative element, closely resemble the corres- 
ponding compounds of oxygen. 

351. Sulphohydric Jicid — Hydrosulphuric Jlcid 
— Sulphuretted Hydrogen. — HS; 1 + 16.1 = 17.1. 
This acid may be prepared by heating one equivalent 
of sesquisulphuret of antimony, in a retort, with three 
equivalents of chlorohydric acid. A sesquichloride of 
antimony and sulphohydric acid are formed, the latter 
of which escapes in the form of a gas. Sulphohydric 
acid is a colourless, transparent gas, which becomes 
a limpid liquid under a pressure of 17 atmospheres. 
It feebly reddens litmus paper, and has a character- 
istic odour like that of putrid eggs. It is highly de- 
leterious to animal life, even when very much diluted 
with atmospheric air. It extinguishes the flame of 
burning bodies, but is itself inflammable, burning 
with a pale blue flame, and at the same time depo- 
siting sulphur, and producing water and sulphurous 
acid. The sp. gr. of this gas is 1.1782. Water ab- 
sorbs its own bulk of this gas, becomes feebly acid, 
and acquires its peculiar taste and odour. It is 
readily decomposed by nearly all the metals and non- 
metallic elements. It may be distinguished from all 
other gases by its peculiar odour, and by forming a 
black sulphuret with silver. 

Sulphur forms another compound with hydrogen, 
a viscid, yellow liquid, of little permanence, which 
is probably a bi-sulphuret of hydrogen. 

352. The Metallic Sulphurets. — The metallic sul- 
phurets are opaque, brittle solids, many of which 
possess a metallic lustre ; they are all fusible and 
crystallizable ; most of them are fixed in the fire, 
and a few are volatile ; some of them are remark- 



METALLIC SULPHURETS. 173 

able for the beauty of their colours ; the protosul- 
phurets are difficult of decomposition ; while those 
containing more than one atom of sulphur are readi- 
ly decomposed. The sulphurets of arsenic, anti- 
mony, tungsten, molybdenum, tellurium, tin, and 
gold, are electro-negative compounds, and true sul- 
phur acids. The combination of several of the met- 
als with sulphur, is attended with the disengage- 
ment of intense light and heat, and when the heated 
metal is exposed to the vapour of sulphur, it exhibits 
all the phenomena of combustion. 

353. The sulphurets of the alkaline metals, potas- 
sium and sodium, are deliquescent and soluble, and 
greedily attract oxygen from the atmosphere. The 
sulphuret of sodium is the colouring principle of the 
celebrated blue mineral pigment, lapis lazuli. 

The tersulphuret of potassium is a solid of a liver- 
brown colour, and is known by the name of liver of 
sulphur. 

354. Sulphuret of potassium, in a state of minute 
division, takes fire at the ordinary temperature. A 
preparation of this kind, called Homberg's Pyro- 
phorus, is made by heating equal weights of per- 
fectly dry and finely powdered sugar and alum, or 
3 parts of lampblack, 4 of dried alum, and 8 of car- 
bonate of potassa. The mixture is to be kept at a 
red heat, in a tube or bottle, until inflammable gas 
ceases to be evolved. It must be kept from contact 
with the air, in which it is spontaneously inflam- 
mable. 

355. The sulphurets of barium, strontium, and cal- 
cium, are soluble in hot water, and form transparent 
crystals, containing water of crystallization. These 
sulphurets, when exposed to the solar ray, absorb 
light, which they emit so copiously in the dark as to 
become luminous, or phosphorescent. Canton's phos- 
phorus is a sulphuret of calcium, which is thus lumi- 
nous, and which is prepared by exposing flowers of 

15* 



174 PRINCIPLES OF CHEMISTRY. 

sulphur and calcined oyster shells for an hour to a 
red heat. 

356. The bisulphuret oj * iron, or iron pyrites, \$ 
one of the most abundant ores of iron. It has a yel- 
low colour, strikes fire with steel, and crystallizes in 
cubes, or some allied forms. 

The sulphuret of zinc is found abundantly in na- 
ture, and is called blende. It is red, brown, yellow, 
or black, with a peculiar resinous lustre. 

The protosulphuret of arsenic is of a ruby red col- 
our; and the sesquisulphuret, of a rich lemon yellow. 
The former is known to mineralogists by the name 
of realgar, and the latter by that of orpiment. They 
are employed as pigments ; undergo sublimation 
without change, and are electro-negative in their re- 
lations to most other sulphurets. 

The bisulphuret of molybdenum is a solid of a 
steel-gray colour, closely resembling graphite. It is 
the ordinary ore of the metal. 

The sesquisulphuret of antimony is the ordinary 
ore of antimony. It crystallizes in rhombic prisms 
and needles, is of a reddish gray colour and a me- 
tallic lustre. The f sulphuret, or persulphuret, is a 
powder of a red colour, occasionally used in phar- 
macy. 

357. The disulphuret of copper is the mineral 
called copper glance. The sulphuret of copper, 
combined with the protosulphuret of iron, forms the 
mineral called copper pyrites. 

The sulphuret of lead is galena, the most abun- 
dant ore of that metal. It crystallizes in cubes, and 
the allied forms, is of a steel gray colour and metal- 
lic lustre. 

The bisulphuret of mercury occurs native, and is 
called cinnabar. It is prepared artificially by fusing 
sulphur with six times its weight of mercury, and 
subliming in close vessels. When this sublimate is 
reduced to powder, it forms the beautiful pigment 
Vermillion. 



THE HYDROGURETS. 175 

The sxdphuret of silver is the mineral called silver 



glance. 



Section III. 

THE SELENIURETS. 

358. Selenhydric Acid. Hydroselenic Acid. — 
H Se; 1+39.6=40.6. This acid exists in the form 
of a gas, which at first has the odour of sulphohy- 
dric acid and then paralyzes for a time the sense of 
smell. It is absorbed freely by water, and the solu- 
tion reddens litmus paper, and gives a brown stain 
to the skin. It is soon decomposed by exposure to 
the air. 

The metallic seleniurets closely resemble the cor- 
responding sulphurets, and do not require a particular 
discription. 

Section IV. 

THE PHOSPHURETS. 

359. Phosphorus combines with several metals, 
and the union is effected by bringing them in con- 
tact at a high temperature. The phosphuret of cal- 
cium is prepared by passing the vapour of phos- 
phorus over red hot lime. It is a solid of a reddish- 
brown colour, which when thrown into water, is 
decomposed, disengaging spontaneously inflammable 
phosphuretted hydrogen gas. 



Section V. 

THE HYDROGURETS. 

360. Sesquihydroguret of Phosphorus. — P 2 H 3 . 
This compound, which is commonly called phosphu- 



176 PRINCIPLES OF CHEMISTRY, 

retted hydrogen, is a colourless gas, with a disa- 
greeable odour, resembling that of garlic. It takes 
fire spontaneously in chlorine gas, is sparingly solu- 
ble in water, and when mixed with atmospheric air 
or oxygen gas, it detonates by the electric spark, or by 
a sudden expansion, as when a tube containing the 
mixture over mercury is quickly lifted a few inches. 

Phosphuretted hydrogen may be prepared by 
heating hydrated phosphorous acid in a retort. Phos- 
phuretted hydrogen gas may also be obtained by 
heating phosphorus in a strong solution of pure 
potassa. The gas obtained by this process takes fire 
spontaneously on coming into contact with atmos- 
pheric air, each bubble, as it rises to the surface of 
the pneumatic bath, exploding with n bright flame, 
and forming a ring of dense white smoke, which 
rises slowly with a graceful waving motion. The 
spontaneous inflammability of the gas prepared in this 
way, is supposed to be owing to the presence of a mi- 
nute quantity of a spontaneously inflammable oxide 
of phosphorus; for it is destroyed by the presence of 
the vapour of any of the carburets of hydrogen, by 
potassium, phosphorous acid, and other substances 
which have a strong affinity for oxygen. The phos- 
phuretted hydrogen, also, which does not possess 
the property, may have it communicated by a slight 
impregnation of nitrous acid gas. 

361. The sesquihydroguret of arsenic is a gas 
highly deleterious to animal life, and analogous to 
the phosphuretted hydrogen in many of its proper- 
ties. 

These gases form crystallizable compounds, analo- 
gous to the compounds of ammonia, with iodohydric 
and bromohydric acids, so that they appear to be 
feeble alkaline bases. 

Hydrogen also forms a compound with tellurium 
which has acid properties. 



THE ALLOYS. 177 



Section VI. 



THE ALLOYS. 



362. The following are the most useful and well- 
known of these compounds. Arsenic renders the 
metals with which it is combined both brittle and 
fusible. One tenth part of arsenic gives to copper a 
white colour, like silver, and renders platinum fusi- 
ble at a heat a little above redness. Two parts of 
tin alloyed with one of lead, fuse at 360°, and are 
called fine solder; coarse solder consists of four parts 
of lead and one of tin, and fuses at 500°. The best 
pewter consists of tin alloyed with small quantities 
of antimony, bismuth, and copper. 

Eight parts of bismuth, five parts of lead, and, 
three parts of tin, form an alloy which fuses at 210°, 
and is called fusible metal. 

Type metal is an alloy of four parts of lead, with 
one part of antimony. 

363. Bronze is an alloy of ten parts of copper, 
with one of tin. Bell metal is composed of eighty 
parts of copper and twenty parts of tin. A small 
quantity of silver increases, while a small portion of 
lead and antimony greatly impairs the sonorousness 
of the compound. The speculum metal of telescopes 
consists of two parts of copper and one of tin. Brass 
is a compound of four parts of copper and one of zinc. 
Tombac, Dutch gold, and pinchbeck, are varieties of 
brass. The white copper or packfong of the Chi- 
nese, or, as it is called in Europe, German silver, is 
an alloy in variable proportions of copper, nickel, 
and zinc, with a small quantity, perhaps an acciden- 
tal impurity, of either lead, cobalt, or iron. 

364. The tinning of copper consists in covering 
that metal with a thin surface of tin, which is ap- 
plied by heating a perfectly clean piece of copper to 



178 PRINCIPLES OF CHEMISTRY. 

the melting point of tin, and then rubbing it over 
with a piece of that metal. 

Sheet iron is converted into an alloy of iron and 
tin by dipping it in melted tin; the latter metal pene- 
trates the whole substance of the iron and forms an 
alloy, uniting some of the most valuable properties 
of its elements. 

Steel forms alloys of remarkable hardness and 
toughness, with exceedingly minute quantities of 
silver, platinum, rhodium, iridium, and osmium. 

The standard silver for coinage contains a thir- 
teenth part of its weight of copper. 

The combination of the other metals with gold 
greatly impairs its malleability and ductility. Cop- 
per gives it a red tint and great hardness. The 
standard gold coin contains a twelfth part of its 
weight of copper. 

365. The combinations of mercury with other 
metals are called amalgams. An amalgam of seven 
parts of tin and three of mercury is used for silver- 
ing glass mirrors. 

The amalgam for exciting electrical machines is 
composed of one part of tin, one part of zinc, and 
two parts of mercury. 

An amalgam of gold and mercury is used for gild- 
ing brass. 



Section VII. 

BINARY COMPOUNDS OF THE SALT RADICALS. 

366. Chlorine, iodine, bromine, and fluorine, con- 
stitute a natural group, possessing the closest affini- 
ties both singly, and in combination, and are all 
characterized by forming true salts with the electro- 
positive, or metallic bases. They have on this ac- 
count been called salt radicals, and these binary salts 



CHLOROHYDRIC ACID. 179 

so closely resembling those of oxygen and sulphur, 
have been called by Berzelius, the haloid salts. 

367. These elements, with the exception of fluo- 
rine, all combine as bases to form powerful oxygen 
acids. They unite with hydrogen to form com- 
pounds, eminently acid in their sensible properties, 
yet having remarkable analogies with the salts. 
Their compounds with each other, and with the 
other electro negative elements are in general either 
neutral, being destitute of either acid, basic or saline 
properties, or they belong to the same class of salt 
radicals as themselves. 

The intimate relations which subsist between them 
will be best exhibited by arranging together their 
compounds with the same base. 

368. Chlorohydric Acid. Hydrochloric Acid. 
Muriatic Acid. — HC1; 1+35.42=36.42. This 
acid may be prepared by decomposing chloride of 
sodium by oil of vitriol. The rationale of the pro- 
ces may be thus stated: — 

Oil of Vitriol. Chloride of Sodium. 



1 Sulphuric acid, 40.1 

~; oxygen 8 
hydrogen 1 — 9 

49.1 



1 Water, "> 1 oxygen 8 



1 Chlorine, 35.42 

1 Sodium, 23.3 



58.72 

1 Chlorohydric Acid. 

1 Chlorine, 35.42 

1 Hydrogen, 1. 



Yield, 

1 Sulphate of Soda. 

1 Sulphuric acid, 40.1 

1 Sodium, 23.3 

1 Oxygen, 8— 31.3 

71.4 36.42 

369. Chlorine and hydrogen gases combine slowly 
in the diffused light of day. But in the direct rays 
of the sun, they combine instantaneously with a 
violent explosion. 

370. Chlorohydric acid is a colourless gas, of a 
pungent odour, and an acid taste. Under a pres- 
sure of 40 atmospheres, and at the temperature of 
50°, it becomes fluid. 



180 PRINCIPLES OF CHEMISTRY. 

It extinguishes burning bodies; is quite irrespira- 
ble, although less irritating than chlorine. 

Chorohydric acid gas has a powerful affinity for 
water. Whenever it escapes into the air, a dense 
white cloud is formed by its combination with the 
vapour of the atmosphere. A piece of ice liquefies 
instantly on being immersed in this gas, and the gas 
rapidly disappears. A long wide jar of the gas being 
inverted, and opened under water, is filled as rapidly 
as if it had been a vacuum. Water absorbs 480 times 
its bulk of this gas, and acquires a density of 1-2109. 
The quantity of real acid contained in any solution, 
may be ascertained by the quantity of carbonate of 
lime it will neutralize. 

When pure, the strong solution of chlorohydric 
acid is a dense colourless fluid, intensely sour, emit- 
ting copious white fumes, and even when very much 
diluted, reddening litmus paper. It combines with 
water in all proportions, and with the disengage- 
ment of heat. It is used in the arts by the name of 
muriatic acid, and is usually of a yellow colour, from 
containing iron. 

371. Chlorohydric acid parts with its hydrogen to 
all substances that readily yield oxygen, and free 
chlorine is disengaged. This takes place when it is 
mixed with nitric acid, in the proportions of their 
atomic weights. The mixture has been called aqua 
regia, and nitro-muriatic acid, and is in fact a solution 
of chlorine, which combines with and dissolves gold, 
and platinum, and the other metals insoluble in the 
strongest acids. 

Chlorohydric acid is composed of equal volumes 
of chlorine and hydrogen, which unite without con- 
densation when mixed and inflamed. Its sp. gr. is 
therefore 1.2694. Its presence may always be de- 
tected by the dense white precipitate which it forms 
with the nitrate of silver. 



FLUOHYDRIC ACID. 181 

372. lodohydric Acid, Hydriodic Acid. — HI; 
1+126.3=127.3. This acid is a colourless gas of the 
sp. gr. of 4.385, with a very sour taste, reddening 
vegetable blues, and having a powerful affinity for 
water. Its odour resembles that of chlorohydric acid, 
and it causes a white fog when it comes in contact 
with the vapour of the atmosphere. Water absorbs 
this gas copiously, and the saturated solution has a 
sp. gr. of 1.7. The solution is readily decomposed 
by oxygen, iodine being set free, and water being 
formed. Chlorine, nitrous acid, and various other 
substances that have an affinity for water and its 
elements, also decompose it. 

373. Bromohydric Acid. Hydrobromic Acid. — 
H Br; 1+78.4=79.4. Bromohydric acid isa colour- 
less gas with an acid taste and a pungent odour. It 
is irrespirable, and powerfully irritates the glottis. 
It is very soluble in water, and the concentrated solu- 
tion is a dense liquid that yields white vapours by ex- 
posure to the air, and possesses strong acid properties. 

374. Fluohydric Acid. Hydrofluoric Acid. — 
HF, 1+18.6S=19.6S. When finely powdered fluor 
spar is mixed with twice its weight of sulphuric acid, 
and distilled with heat from a leaden retort into a 
leaden receiver surrounded with ice, liquid fluohy- 
dric acid is collected in the latter. 

Fluohydric acid at 32° F. is a colourless fluid, 
which is dissipated at the ordinary temperature in 
dense white fumes. Its specific gravity is 1.0609, 
which may be raised to 1.25 by the addition of water. 
Its affinity for water is so great that the combination 
is accompanied with a hissing noise, as when red 
hot iron is quenched in water. 

Its vapour is much more irritating and pungent 
than chlorine, and it is so destructive of animal mat- 
ter that a drop of the liquid acid no larger than the 
head of a pin instantaneously disorganizes the skin 
and causes a malignant ulcer. 

16 



182 PRINCIPLES OF CHEMISTRY. 

Fluohydric acid has a strong, sour taste, neutra- 
lizes alkalies, reddens litmus paper, and is a power- 
ful acid. It acts energetically on glass, and on some 
of the metals. 

375. The chlorides, bromides, and fluorides of 
sulphur and of phosphorus, are dense, acrid, vola- 
tile, fuming liquids; and their iodides, solids of a 
grayish black or orange colour, and all of them are 
readily decomposed. 

376. The chloride, and bromide, of Silicon, Si Cl 3 , 
SiBr 3 , are dense, volatile, transparent liquids, 
which are resolved by water into silicic acid, Si 3 , 
and chlorohydric and bromohydric acids, 3HC1, 
3HBr. 

377. The Fluoride of Silicon, Si F 3 , is a colour- 
less, transparent gas, of the sp. gr. of 3.611, which 
extinguishes flame, irritates the lungs, and destroys 
animal life. It is instantly decomposed by contact 
with water — four atoms decomposing three atoms of 
water, forming one of silicic acid, Si 3 , and one of 

fluo silico hydric acid, H 3 Si 2 F 9 or 2 Si F 3 +3HF. 
Water absorbs 365 times its volume of this gas,and the 
resulting liquid has a strong, acid taste, and reddens 
litmus paper. In this process the silicic acid ap- 
pears as a fine, semi-transparent film, which invests 
the mouth of the tube, and forms a continuous cylin- 
der from it to the surface of the water. 

The fluohydric acid unites with the remaining 
fluoride to form the acid above described. This acid 
combines with the metallic bases, forming a series of 
tri-basic fluo-silicates or of double fluorides, the for- 
mula for which is M 3 +Si 2 F 9 , or 2 Si+F 3 +3MF. 
V 378. Chlorine and fluorine unite with boron, BC1 3 
BF 3 , and form gases which are rapidly absorbed 
and decomposed by water. The former is resolved 
into boracic and fluo boro hydric acids. The changes, 
and the resulting acids, closely resemble those de- 
scribed above. 



OF SALTS. 183 

The metallic chlorides, iodides, bromides, and 
fluorides, form the sub class of haloid salts, and will 
be considered in the following chapter. 



CHAPTER IV. 

OF SALTS. 

Section I. 

GENERAL VIEWS. 

379. The preceding bi-elementary compounds 
differ greatly from each other in regard to their che- 
mical energies. Some of them, as the peroxides of 
lead and manganese, are -chemically indifferent, and 
do not unite either with acids or alkalies. On the 
other hand, the affinities of some of them are of 
great energy, and have a wide range. These affini- 
ties are, in great measure, restricted to the limits of 
their respective genera. Electro-negative oxides, for 
example, attract and combine with electro-positive 
oxides, and appear to be indifferent to the electro- 
positive chlorides, iodides, bromides, &c. The few 
anomalous cases which are exceptions to this, do not 
impair it as a general law. These secondary com- 
pounds belong to, and form by far the larger portion 
of the class of bodies called salts; and they are na- 
turally divided into orders according to their proxi- 
mate electro-negative element. 

380. Nearly all the salts are solid at common 
temperatures. They are generally crystallizable and 
transparent. Their colour depends in general upon 
that of their elements. 

The alkaline salts have a sharp, saline, or bitter 
taste, frequently producing a sensation of coldness in 



184 PRINCIPLES OF CHEMISTRY. 

the mouth. The metallic salts, such as those of cop- 
per, mercury, and silver, generally have a nauseous 
metallic taste. Salts are mostly soluble in water, 
although the rate of solubility differs greatly, and is 
variably affected by heat. Some do not dissolve 
in a smaller portion of boiling, than of temperate 
water; while others are soluble in a much smaller 
quantity of the former than of the latter. The most 
remarkable example of this is the sulphate of soda, 
the crystals of which are insoluble at 0°F., and dis- 
solve in less than one third their weight of water at 
91.5°, while an increase of heat beyond this tempera- 
ture lessens their solubility. The boiling point of a 
saturated solution of any salt is always higher than 
that of pure water, and increases with the affinity 
of the salt for that menstruum. Salts which have 
a strong affinity for water, attract moisture from the 
air and become liquid; such salts are said to be de- 
liquescent. Others remain dry at the usual state of 
the atmosphere, but attract moisture in a damp air. 
Salts which dissolve more copiously in hot than in 
cold water, are deposited in regular crystals by the 
gradual cooling of the solution. Crystals are pro- 
cured from those saturated solutions which are as 
strong when cold as when heated, by evaporating 
the water in a continued heat, or in a current of dry 
and warm air. The slower the cooling and evapo- 
ration, the larger and more perfect will be the crys- 
tals. 

381. Many salts, during the act of crystallization, 
combine with and solidify a certain portion of water, 
which is called the water of crystallization. This 
quantity varies with different salts, but is uniform in 
those crystals of the same salt, which agree in form. 
Many salts which contain water of crystallization, 
part with it in a warm and dry atmosphere, and 
effloresce or crumble into a white powder. 

Crystals which contain no water of crystallization, 



OF SALTS. 185 

or are anhydrous, upon being heated, frequently 
break into smaller fragments, which fly off with a 
sort of explosion. They are said to decrepitate, and 
the phenomenon is owing to their brittleness and un- 
equal expansion by heat. 

382. A saturated solution of any salt is still capa- 
ble of dissolving another soluble salt, provided the 
two do not decompose each other. This law has 
been advantageously applied to the purification of 
crystals, by washing them with a saturated solution 
of the same salt, which removes all the soluble sa- 
line impurities they may contain. 

383. It has become a question among chemists, 
what is the real constitution of a salt; and there is 
reason to believe that the old theory which supposed 
them to be constituted of an acid and a base, must 
yield to views which are the result of a wider and 
more profound generalization. 

384. The perfect resemblance in their chemical 
relations, of those salts which are bi-elementary 
compounds of the first order, to those which are of 
a secondary order, is a strong presumption in favour 
of a similarity of constitution. Chloride of sodium, 
for example, is a true salt, in which the metal so- 
dium is combined with a simple electro-negative 
element. We have many examples in organic che- 
mistry of very complex compounds, acting the same 
part as the simple elements, passing from one com- 
bination to another, without undergoing decomposi- 
tion, although incapable themselves of existing ex- 
cept in combination. Such compounds, on the com- 
mon theory of salts, we must suppose the nitric, and 
chloric, and various other acids, to be; for they are 
incapable of existing except in combination with 
water, or some other base. 

385. If then the chloride of sodium be the type of the 
order, a salt may be regarded as a binary compound 
of a metal with either a simple or a complex radical; 

16* 



186 PRINCIPLES OF CHEMISTRY. 

and the. oxygen of an oxygen salt, instead of being 
distributed between the base of the acid and the 
metal, is wholly united to the former, so as to con- 
stitute the electro negative-element of the salt. Thus, 
for example, sulphate of soda will no longer be re- 
presented by the symbol Na 0+S0 3 , but by the 
symbol Na+So 4 . 

386. There are many facts which render this view 
highly probable. All the acids, in what may be 
called their active state, contain water, while the 
anhydrous acids exhibit a remarkable indifference to 
combination. Such is the fact with regard to sul- 
phuric acid, the most energetic of the class. It does 
not redden litmus paper. It shows little disposition 
to unite with the dry alkalies or alkaline earths, un- 
less they be strongly heated. On the other hand, 
when dry baryta is presented at common tempera- 
tures to oil of vitriol, they unite with such force as 
to become ignited. On this theory the hydrated 
acids belong essentially to the same class as the salts, 
and pass into salts by the substitution of an atom of 
metal for the atom of hydrogen. Oil of vitriol, for 
example, will be represented by H+S0 4 , and the 
three acids of phosphorus by H+P 2 6 , H 2 +P 2 7 
and H 3 + P 2 8 , and their salts by M+S0 4 , M+P 2 
6 , M 2 +P 2 7 andM 3 P 2 8 . 

387. The decisive proof ot the correctness of this 
theory is to be found in the electrolytic decomposi- 
tion of salts. The same current of electricity, it is 
well known, will decompose an equivalent of any 
binary compound. When a solution of sulphate of 
soda is placed in the voltaic circuit, both sulphuric 
acid and oxygen are found at one electrode, and 
soda and hydrogen at the other; from which it might 
be inferred that the electric force had been divided 
between the salt and the water, and that both had 
been decomposed by direct electrolytic action. If 
this were the case, the sum of the two decompose 



OF SALTS. 187 

tions should represent the decomposing energy of 
the current. But it is found that full equivalents 
both of the salt and the water have been decom- 
posed, which is wholly inexplicable on the old theo- 
ry. If the real constitution of sulphate of soda be 
Na+S0 4 , this result can be clearly explained. The 
sodium, upon being disengaged, instantly decom- 
poses an atom of water, and soda and hydrogen are 
evolved at the negative electrode. The negative 
element of the salt being incapable of a separate 
existence, seizes upon the hydrogen of an atom of 
water to form oil of vitriol H+S0 4 , setting its oxy- 
gen free, and the two are evolved at the positive 
electrode. 

388. The decomposition of the water is thus due 
to the secondary action of the current, and the quan- 
tity of the salt decomposed is in exact accordance 
with the electrolytic law. 

389. In like manner, when a solution of sulphate of 
copper is decomposed by electrolytic action, metallic 
copper is evolved at the negative, and acid and water 
at the positive electrode, and the quantity of copper 
separated exactly represents the electric energy of the 
battery. These cases are precisely like those of the 
metallic chlorides, and they must be regarded as 
decisive proofs of the truth of the new theory. 

390. These facts throw new light upon this de- 
partment of chemistry, by the simplicity and beauty 
of the general laws which they establish. The 
great law of saline combination is, that in the same 
genus of salts, the number of equivalents of the elec- 
tro-negative element in the base bears a constant 
ratio to the number in the acid. This ratio in the 
sulphates is as one to three, and the sulphates of the 
susquioxides are all ter-salts, and those of the deutox- 
ides bi-salts: thus maintaining the same proportion 
of one to three between the oxygen of the base 
and the acid. This law is a necessary consequence 



1 88 PRINCIPLES OP CHEMISTRY. 

of the new theory; for a salt, and an acid in its active 
state, being both of them compounds of an elec- 
tro-negative element, the one with a metal, and the 
other with hydrogen, the conversion of the latter into 
the former is effected by the simple replacement 
of the hydrogen by the metal. This takes place 
through the mutual decomposition of the acid and 
oxide, the hydrogen and oxygen of which form wa- 
ter; while their other elements unite to form the salt. 
A sesquioxide, therefore, requires three, and a deut- 
oxide two atoms of acid to neutralize it. 

391. Monobasic and Poly basic Acids. — Some of 
those definite compounds which acids form with 
water, must be regarded as essential modifications 
of the acid. Thus the metaphosphoric acid, which 
contains an atom of water, is represented by H+P 2 
6 ; the pyro or bi-hydrated phosphoric acid is H 2 + 
P 2 7 ; and the common or ter-hydrated acid is H 3 + 
P 2 8 . This view of their composition explains the 
nature of the combinations into which they enter. 
The metaphosphoric acid can form but one class of 
salts, namely, that containing one atom of metal, 
and it is therefore called a monobasic acid. The 
salts of the pyrophosphoric acid always contain two 
electro-positive or basic atoms, in which one or both 
atoms of hydrogen are replaced by a metal. The 
formula of its salts is M 2 +P 2 T or MH+P 2 7 . 

The ter-hydrated acid is a tribasic acid, for it forms 
salts which always contain three atoms of base, in 
which one, two, or all the atoms of hydrogen may 
be replaced by a metal. The formula of its salts will 
thereforebeM 3 +P 2 8 ,M 2 H+P 2 8 ,orMH 2 +P 2 8 , 
in all which formula3 M represents the metallic base. 

It is not necessary that the same metal should 
replace all the hydrogen in these bi and tribasic 
salts. The tribasic phosphoric acid forms, for ex- 
ample, a phosphate of magnesia, alumina and water 
represented by MgAlH+P 2 8 . 



OF SALTS. 189 

This division of acids into monobasic and poly- 
basic, is of great importance to the right understand- 
ing of the complicated details of this department of 
organic chemistry. 

392. Basic and Constitutional Water. — The 
manner in which water enters into the constitution 
of acids and salts, greatly modifies the character and 
chemical relations of these compounds. The fol- 
lowing examples will serve to unfold the laws which 
govern these combinations. 

Sulphuric acid forms at least three definite com- 
pounds with water. The first is the common oil 
of vitriol, which must be regarded as HS0 4 ; the 
second is a hydrate, and the third a bi-hydrate of the 
first, and their formulae are HS0 4 +Aq, and HS0 4 + 
2Aq. 

So, likewise, the definite combinations of nitric 
acid with water, must be regarded as HN0 6 ,HN0 6 
+Aq, and HN0 6 +2 Aq. 

393. Most salts in the act of crystallizing, combine 
with and solidify a definite quantity of water, which 
is called water of crystallization. 

Thus, sulphate of zinc crystallizes with seven atoms 
of water. A portion of this exists in a different state 
of combination from the remainder, for when heated 
to 212°, the sulphate of zinc parts with six atoms, 
but retains the seventh until heated to 410°. This 
last atom is termed by Graham constitutional water, 
and it is always regained by the salt when moistened. 

This atom of constitutional water may be replaced 
by an atom of a new salt, as in the present case, by 
sulphate of potassa. The sulphate of zinc unites 
with the sulphate of potassa to form the double sul- 
phate of zinc and potassa, and this salt always crys- 
tallizes with six and not with seven atoms of water 
of crystallization, and it parts with them all at 212°. 

The constitution of the two sulphates may be thus 
stated: HO+ZnS0 4 +6 Aq,and KS0 4 +ZnS0 4 +6Aq; 



190 PRINCIPLES OP CHEMISTRY. 

so that the constitutional water of the first salt, re- 
presents the sulphate of potassa in the second. 

394. As another neutral salt, of the same family, 
can take the place of the constitutional water in the 
above salt, so the oxide of the metallic base of the 
salt, may replace a part or the whole of its water of 
crystallization. Thus, for example, the following 
modifications of sulphate of zinc have been obtained. 



ZnSCT+7HO. 



ZnS0 4 +3ZnO+4HO. 



ZnS0 4 +5ZnO+2HO. 



ZnS0 4 +7ZnO. 

395. So, likewise, the hydrated nitric acid, which 
is represented by HN0 6 +3HO, may be regarded as 
a hydrated nitrate of hydrogen. When an atom of 
copper replaces the hydrogen, we have the common 
nitrate of copper, CuN0 6 +3HO; and there is also 
a basic nitrate of copper, in which two atoms of 
water are replaced by two of protoxide of copper, 
CuN0 6 +2CuO+HO. 

396. This replacement of water by a metallic 
oxide, takes place also in the haloid salts. Thus we 
have an oxy-chloride of copper, CuCl+3CuO and 
an oxy-chloride of mercury, HgCl-f-3 HgO, which 
are exactly analogous to the combinations of the 
same chlorides with oxide of hydrogen, CuCl+3 
HO, and HgCl+3HO. 

397. These views enable us to understand the 
true constitution of the bi-salts of the protoxides, 
of which an atom of water is always an essential 
element. Oil of vitriol may be regarded as a sul- 
phate of hydrogen, HS0 4 and the bi-sulphate of 
copper as HS0 4 +CuS0 4 . So, likewise, the bi-car- 
bonate of potassa is in reality the double carbonate 
hydrogen and potassium, HC0 3 +KC0 3 . 

398. Salts of different acids with the same base, 



OF SALTS. 191 

may combine to form double salts, as the oxalate 
and nitrate of lead, and there are a few examples of 
double salts, containing two acids and two bases. 

399. There are salts containing two or more atoms 
of acid and one of base, which differ essentially from 
the bi-salts above described, in containing the acid 
in an anhydrous form. Thus there is an anhydrous 
bi-chromate and ter-chromate of potassa, represented 
by K Cr0 4 +Cr0 3 ,and K Cr0 4 +2Cr0 3 . The chromic 
acid likewise combines with neutral haloid salts, for 
we have its anhydrous compound with chloride of 
sodium, and with chloride of potassium, the for- 
mulae of which are Na Cl+2Cr 3 , and by KC1+2 
Cr 3 . In these compounds the chromic acid seems 
to represent the water of crystallization of salts, which 
it replaces in the same manner as does the oxide of 
zinc. 

400. These views of the constitution of salts, are 
confirmed by the nature of the organic compounds, 
which present many striking proofs of the same great 
law of substitution. It is probable that the estab- 
lishment of this theory will render it necessary in 
the end, to remodel the language of chemistry. The 
present nomenclature is sufficiently expressive for 
ordinary purposes, and we possess in the invention 
of symbols, so accurate and concise a mode of repre- 
senting the actual state of combination, that there is 
no pressing necessity for a change. The science is, 
moreover, at the present time, in a state of transi- 
tion, which renders any attempt to reform its lan- 
guage premature. 

401. Isomorphism. — It has been shown that all 
crystalline bodies belong to one of the six systems of 
crystallization already described, and that the same 
crystalline form must therefore be common to a great 
number of bodies. 

When solutions of two salts, the crystals of 
which belong to the same system, and agree in the 



192 PRINCIPLES OF CHEMISTRY. 

length of their axes, are mingled and evaporated, 
the crystals which they form are found to consist of 
variable quantities of the two salts. 

402. There is a very natural group of double sul- 
phates, of which common alum is the type, and 
which consist of an atom of a tersesquisulphate 
combined with an atom of protosulphate. They 
agree in possessing a sweetish astringent taste, in 
reddening litmus paper, and in crystallizing in regu- 
lar octohedrons. The base of the tersulphate in 
these alums may be the sesquioxide of alumina, of 
iron, of chrome, or manganese, and the base of the 
protosulphate, either potassa, soda or, ammonia. It 
would seem that when the elements of these various 
alums are present in solution, they may all contri- 
bute to the formation of a salt, which shall be a 
genuine alum, and yet consist of proportions alto- 
gether uncertain and accidental of the several species; 
the only condition essential to its formation being, 
that each atom consist of an atom of a protosulphate 
combined with an atom of a tersesquisulphate. 

403. The application of this law to the science of 
mineralogy, bids fair to reduce its apparent confu- 
sion into order. There are many genera of minerals, 
of which hornblende or augite is an example, which 
are framed from the agreement of certain minerals 
in their forms of crystallization, and other mineral- 
ogical characters. The application of analysis to 
identify this agreement in external characters, threw 
the whole matter into a confusion which is only to 
be cleared up by this theory of the nature of the 
double isomorphous salts. Thus, augite was found 
to be a double salt, containing an atom of bisilicate 
of lime, combined with an atom of bisilicate of mag- 
nesia, which is the composition of that species of 
augite caMed-diopside. In the species called sahlite, 
a portion, and in another species, the whole of the 
magnesia is replaced by protoxide of iron; in the 



THE HALOID SALTS. 193 

mineral called hypersthene the iron replaces the 
lime and not the magnesia; and the mineral called 
basaltic hornblende is a mixture of the bisilicates of 
lime, magnesia, iron, and alumina. 

404. This property of isomorphism appears to 
depend upon similarity of atomic constitution. It is 
possessed, for example, by those oxides which con- 
tain the same number of atoms of oxygen and of 
base, and is carried throughout their similarly con- 
stituted compounds. Thus sulphuric, selenic, tel- 
luric, chromic, and manganic acids, contain three 
atoms of oxygen to one of base, and all their cor- 
responding salts crystallize alike. Another well 
marked isomorphous group is the sesquioxides of 
iron, manganese, chrome, and aluminium. Phos- 
phoric and arsenic acids constitute a third; and the 
protoxides of iron, manganese, copper, cobalt, nickel, 
zinc, magnesia, and lime, a fourth group. 

405. Although that similarity of atomic constitu- 
tion, of which the isomorphism of complex com- 
pounds is a result, must in the case of the elements 
and their simpler combinations, be accounted acci- 
dental; yet we find its value, as an indication of 
close affinity, to increase with the complexity of con- 
struction, and to obtain in organic chemistry a high 
value as an index of the properties of bodies. 



Section II. 

THE HALOID SALTS. 

406. The binary compounds of the salt radicals 
with the alkaline, and earthy alkaline metals, are, 
with the exception of some of the fluorides, highly 
soluble crystalline sapid substances. 

The chlorides and fluorides of some of the most 
17 



194 PRINCIPLES OF CHEMISTRY, 

fixed metals are volatile fuming liquids or gases. 
The bromides and iodides are less volatile and liquid. 
Many of them are remarkable for the extreme bril- 
liancy of their colour. 

Their affinity for the metals is so great that their 
direct combination often presents all the phenomena 
of combustion. No heat that has yet been applied 
is capable of decomposing some of the chlorides. 
Sulphuric acid decomposes all these salts with the 
exception of the chlorides of silver and mercury. 

THE CHLORIDES. 

407. The chloride of potassium forms anhydrous 
cubic crystals, insoluble in alcohol, soluble in three 
parts of cold, and in still less of hot water, and hav- 
ing a saline, bitter taste. 

The chloride of sodium is common sea and rock 
salt, and is one of the most abundant substances in 
nature. 

It fuses at a red heat, is colourless and trans- 
parent, has a pure saline taste, is insoluble in pure 
alcohol, dissolves in 2J times its weight of both boil- 
ing and cold water, and crystallizes in anhydrous 
cubic crystals. It is a wholesome condiment, and 
from its powerful antiseptic properties is much used 
in preserving meat from putrefaction. It is much 
used in the arts for various purposes. 

408. The chloride of barium is insoluble in alco- 
hol, and dissolves in more than twice its weight of 
water. It cystallizes in flat four-sided tables, con- 
taining two atoms of water. 

The chloride of strontium is soluble in alcohol 
and in water, and crystallizes in colourless prisms, 
containing nine atoms of water. Its alcoholic solu- 
tion burns with a crimson flame. 

The chloride of calcium is remarkable for its great 
solubility in and affinity for water. It may be ob- 



THE CHLORIDES. 195 

tained in transparent prismatic crystals, containing 
six atoms of water, which are driven off at a red 
heat. It is much used for the preparation of freez- 
ing mixtures, and is very soluble in alcohol. 

The chloride of magnesium is a transparent, co- 
lourless mass, soluble in alcohol and water, and, 
like the chloride of calcium, highly deliquescent. 

The sesquichloride of aluminium has a highly 
crystalline lamellated structure, and a greenish-yel- 
low colour, partially translucent, resembling talc; 
it is fusible and volatile at about 212°, and deliques- 
cent in the air. 

409. Manganese forms a protochloride, which is 
a pink-coloured, lamellated mass, and a -| chloride, 
or perchloride, which is a gas of a greenish copper 
colour, that condenses at about zero into a greenish- 
brown liquid. 

Iron forms a protochloride which is a white crys- 
talline solid, forming with water a greenish solution 
that yields crystals of the same colour. Its sesqui- 
chloride is volatile at 212°, and forms red iridescent 
crystals, soluble in water, alcohol, and ether. 

The chloride of zinc is a colourless, transparent 
solid, that fuses at 212°, sublimes at a red heat, and 
deliquesces in the open air. 

410. The protochloride of tin is a gray solid, of 
a resinous lustre, which fuses below redness, is solu- 
ble in water, and crystallizes in transparent prisms. 

The bichloride of tin is a limpid fluid, which emits 
dense, white fumes in the open air, boils at 248°, 
and forms a solid hydrate. It is much used in dye- 
ing, as a mordant for fixing and brightening certain 
colours. 

The anhydrous chloride of cobalt is blue, and its 
hydrate is of a pink colour. Owing to this property 
its solution forms a sympathetic ink, which is colour- 
less when cold and moist; while it is of a beautiful 
blue colour when heated. 



196 PRINCIPLES OF CHEMISTRY. 

Antimony forms a sesquichloride, a bichloride, 
and a terchloride. The sesquichloride is a soft deli- 
quescent solid, liquefied by a gentle heat, and crys- 
tallizing in cooling. The bichloride, or f chloride, 
is a compound of little permanence; and the per- 
chloride, or f chloride, is a transparent fuming vola- 
tile liquid. They are all decomposed by being dis- 
solved in water. 

The chloride of lead is a semi-transparent solid, 
fusible at a heat below redness, and having a sp. gr. 
of 5.13. 

411. The protochloride of mercury is the well- 
known medicine, calomel It is generally in the form 
of a white powder, which sublimes without fusion, 
at a heat below that of redness. The sublimate is a 
semi-transparent crystalline mass. Its sp. gr. is 7.2; 
it is insoluble in water, and is decomposed by solu- 
tions of the pure alkalies, the black protoxide of 
mercury being formed. 

412. The bichloride of mercury, or as it is com- 
monly termed corrosive sublimate, is generally pre- 
pared by subliming a mixture of one equivalent 
of the bisulphate of mercury, with two equivalents 
of chloride of sodium. The oxygen and the sul- 
phuric acid combine with the sodium; one atom of 
bichloride of mercury is sublimed, and two atoms of 
sulphate of soda remain in the vessel. The proto- 
chloride is usually obtained from the bichloride, by 
triturating one equivalent of mercury with one of the 
bichloride, until all the metallic globules disappear, 
and then subliming the mixture. When mercury is 
heated in chlorine gas, it burns with a red flame, and 
is converted into bichloride. 

Bichloride of mercury is a semi-transparent crys- 
talline colourless solid, of a nauseously metallic, acrid, 
and burning taste. Its sp. gr. is 5.2; it fuses at a 
heat below that of redness, is soluble in twenty times 
its weight of cold, and twice its weight of boiling 






CHLORIDE OF SILVER. 197 

water, and crystallizes in transparent prisms. It is 
also soluble in these proportions in alcohol and ether. 
It is one of the most virulent poisons known. The 
most delicate method of testing the presence of cor- 
rosive sublimate, is to place a drop of the suspected 
liquid on polished gold and touch the moistened sur- 
face with an iron or steel point, when the part 
touched instantly becomes white, owing to the for- 
mation of an amalgam of gold. 

The bichloride forms with alkalies an orange-red 
precipitate, which is the deutoxide of mercury. 

Many animal and vegetable substances have the 
property of converting the bichloride more or less 
rapidly into calomel. This change is almost instan- 
taneously effected by albumen, and the solution of 
the white of eggs is consequently an antidote to the 
poisonous effects of corrosive sublimate. 

413. Chloride of silver ', as prepared by precipita- 
tion, is a white powder which gradually darkens in 
diffused day-light, becomes black in the direct rays 
of the sun, and is instantly blackened by the chemi- 
cal ray at and beyond the violet extremity'of the 
spectrum. It is insoluble in water, and most acids, 
but dissolves in a solution of ammonia. At 500° it 
fuses, and cools into a semi-transparent horny mass 
of the sp. gr. of 5.5. 

The protochloride of gold is an insoluble yellow 
powder, which loses its chlorine, and is converted 
into metallic gold at a red heat. 

The terchloride of gold may be obtained in fusi- 
ble prismatic crystals, of a ruby-red colour. They 
are deliquescent and soluble in water, alcohol, and 
ether. The latter fluid withdraws the terchloride 
from its solution in water, and metallic gold is gradu- 
ally deposited from this ethereal solution in crystal- 
line flakes. At 400° it begins to part with its chlo- 
rine, and is converted, by increasing the heat, into 
the protochloride. 

17* 



198 PRINCIPLES OF CHEMISTRY. 



THE IODIDES. 

414. Iodine has a powerful affinity for metals, 
although weaker than that of chlorine, oxygen, and 
bromine. 

The iodides of the metallic bases of the alkalies 
and alkaline earths, like the corresponding chlorides, 
are eminently saline in their properties. They are 
white, semi-transparent, crystalline, soluble solids, 
saline to the taste, and decomposed by sulphuric and 
nitric acids. The iodides of the metallic bases of the 
earths are unknown. 

415. Iodine forms with iron a protoiodide, which 
is a deliquescent, crystalline mass, of an iron-gray 
colour and metallic lustre. 

The sesquiodide is a deliquescent, volatile red 
compound, soluble in water and alcohol. 

The iodide of lead is obtained in crystalline scales 
of a brilliant yellow colour, forming a colourless so- 
lution in boiling water. 

The protoiodide of mercury is an insoluble green 
powder; the sesquiodide is a yellow powder; and the 
biniodide is a powder of a rich scarlet colour, more 
beautiful though less permanent than vermillion. 
At 400° it fuses and sublimes. The vapour con- 
denses in transparent yellow crystals, which assume 
a brilliant scarlet hue when cooled below 60°, or 
when rubbed or scratched with a sharp point. 

THE BROMIDES. 

416. Bromine has a powerful affinity for the 
metals, uniting with many of them with the extrica- 
tion of intense light and heat. The properties of 
only a few of these compounds have been as yet 
examined. The bromides of potassium, sodium, 
barium, calcium, and magnesium are, like the cor- 



THE SALTS OF SULPHUR. 199 

responding chlorides and iodides, eminently saline 
in their qualities. They closely resemble the respec- 
tive chlorides. 

THE FLUORIDES. 

417. The fluoride of potassium crystallizes in 
cubes, is sharply saline to the taste, deliquescent, 
and very soluble in water. 

The fluoride of sodium forms anhydrous cubic 
crystals, and is sparingly soluble in water. Both these 
fluorides destroy glass by combining with the silica. 

The fluoride of calcium is the well-known fluor, 
or Derbyshire spar, a mineral remarkable for its 
beauty and variety of colours, and the regularity of 
its crystalline forms. It crystallizes in cubes and 
octohedrons, is insoluble in water, fuses at a red heat, 
and is decomposed by sulphuric acid. 

The perfluoride of manganese is a gas of a bright 
greenish yellow colour, that becomes of a beautiful 
purple red when mixed with the atmosphere ; it is 
freely absorbed by water, and acts instantly on glass. 



Section III. 

THE OXYGEN SALTS. 

418. The Salts of Sulphur. — These salts are the 
hyposulphites, represented by M,S 2 3 ; the sul- 
phites, M, SO 3 , the hyposulphates,M, S 2 6 ,and the 
sulphates M, S0 4 . 

Of these salts, the sulphates are the only ones of 
importance. 

419. The presence of a soluble sulphate may al- 
ways be detected by chloride of barium, which 
occasions a white precipitate, insoluble in acids or 



200 PRINCIPLES OF CHEMISTRY. 

alkalies. An insoluble sulphate may be detected by 
exposing it, mixed with three times its weight of 
carbonate of soda, to a red heat. Double decompo- 
sition takes place, and a soluble sulphate of soda is 
formed, from which chloride of barium separates the 
acid. 

Several of the sulphates, as those of baryta and 
lead, are altogether insoluble; those of lime and 
strontia are very sparingly soluble, and nearly all 
the others freely soluble in water. 

All the sulphates, except those of the fixed alka- 
lies and alkaline earths, are decomposed at a white 
heat; and when subjected to the combined action of 
carbon and heat, they are all converted into metallic 
sulphurets. 

420. The sulphate of lime is found native in con- 
siderable quantities, and is known by the name of 
gypsum, or plaster of Paris. In its native state it 
usually contains two atoms of water, and fuses in 
its own water of crystallization; by exposure to a 
continued heat the water is driven off and the an- 
hydrous sulphate remains in the form of a white 
powder. In this state it has a powerful affinity for 
water, eagerly combining with it into a compact 
solid mass. This property renders calcined gypsum 
very useful in taking casts and moulds. What is 
remarkable is, that by no process can we communi- 
cate this property of solidifying water, to gypsum 
which has once undergone the process. 

The sulphate of baryta is also found abundantly 
in nature, and is called heavy spar. 

421. The sulphate of soda, under the name of 
Glauber's salts, and that of magnesia, as Epsom 
salts, are much used as safe cathartic or purgative 
medicines. 

The sulphate of the protoxide of iron is called 
copperas or green vitriol, and that of the protoxide 
of copper, blue vitriol. 



THE SALTS OF NITROGEN. 201 

The double sulphate of soda and lime is the mine- 
ral called glaaberite. 

The double sulphates that constitute alum have 
already been spoken of. 

422. The Salts of Nitrogen* — These are the hy- 
ponitrites, M.N0 4 , the nitrites, M,N0 5 , and the ni- 
trates, M, N0 6 . 

423. The nitrates are all soluble in water, and it 
is for this reason difficult to detect their presence by 
any reagent. When chlorohydric acid is mixed 
with a nitrate, it is decomposed and chlorine is dis- 
engaged; the presence of which may be ascertained 
by its dissolving gold leaf. This test is not, how- 
ever, a decisive one, where there is ground to sus- 
pect the presence of iodates, chlorates, seleniates, or 
bromates, as they exhibit the same appearance. 
The vegetable alkali, morphia, acquires an orange- 
red colour by the action of nitric acid, and may be 
used as a test of the presence of any of its combina- 
tions. The supposed nitrate is heated in a test tube 
with a drop of sulphuric acid, and then a crystal of 
morphia is added. 

The only means of obtaining nitric acid, is by the 
decomposition of some one of its salts. 

The nitrates of potassa, soda, lime, and magnesia, 
are found native, and their nitric acid appears to be 
formed, either during the decomposition of animal and 
vegetable bodies, or by the same kind of corpuscular 
action by means of which platinum promotes the 
combination of oxygen and hydrogen. They are 
found to be spontaneously generated in the soil in 
various parts of the world, and are artificially pre- 
pared by mixing calcareous earth with animal and 
vegetable remains. Nitric acid is generated during 
the decomposition of the organic matter, and com- 
bines with the earthy or alkaline bases which are 
present. 

424. All the nitrates are decomposed by a high 



202 PRINCIPLES OF CHEMISTRY. 

temperature, and yield oxygen and nitrous acid, 
which cause the rapid combustion of any combusti- 
ble or oxidable bodies that may be present. The 
phenomenon is called deflagration, and is generally 
performed by mixing equal quantities of the inflam- 
mable substance and the nitrate, and projecting them 
in small portions into a red-hot crucible. 

The most useful of these salts, is nitrate of potassa, 
or nitre, as it is usually termed. It is a powerful 
antiseptic, and is much employed in preserving meat 
and animal matters from decomposition. It is used 
in the preparation of nitric acid, and in the manu- 
facture of gunpowder, which is prepared by the in- 
timate trituration and levigation together of 12.5 
parts of sulphur, 12.5 of charcoal, and 75 of nitre. 
The theoretic constitution of the best gunpowder is 
S,C 3 KN0 6 , the decomposition of which produces 
sulphuret of potassium, and more than 1000 times 
its volume of nitrogen and carbonic acid gas. 

425. The nitrate of silver is used as a caustic under 
the name of lunar caustic. It communicates a deep 
brown indelible stain to vegetable and animal sub- 
stances, and is the basis of most of the indelible inks. 

426. The Salts of Chlorine. — These are the hypo- 
chlorites, M, CI 2 , the chlorites, M, CI 5 , the chlo- 
rates, M, CI 6 , and the perchlorates, M, CI 8 . 

427. The hypochlorite of lime is supposed to be 
the active element of the bleaching powder, which 
is sold under the name of chloride of lime. This 
powder, when properly prepared, consists of chlo- 
rine, oxygen, and lime, in their atomic proportions, 
and is probably a mixture of the hypochlorite of 
lime and the chloride of calcium, which may be re- 
presented by Ca CI 2 +Ca CI. 

428. The chlorates contain the same proportions 
of oxygen in the acid and base as the nitrates: viz. 
MO+C10 5 ; and are very analagous to them. They 
are decomposed at a red heat, being resolved into a 



THE SALTS OF PHOSPHORUS. 203 

metallic chloride, and yielding all their oxygen in the 
gaseous form. They deflagrate with inflammable 
substances more violently than the nitrates; a mix- 
ture of one part of sulphur, and three parts of chlorate 
of potassa, explodes when struck between two hard 
substances. A mixture of this, with a little charcoal 
or gunpowder, is sometimes used for the percussion 
caps for guns, but it is said to corrode the lock. A 
sulphur match, coated with a mixture of gum or 
sugar and chlorate of potassa, takes fire from the 
decomposition of the chlorate, when it is dipped in 
sulphuric acid, and is much used as a means of ob- 
taining fire. 

The chlorates are mostly very soluble salts. 

The chlorate of potassa is obtained by passing 
chlorine gas through a mixture of two parts by 
weight of carbonate of potassa, and one part of hy- 
drate of lime. By digesting the mass in water when 
saturated with chlorine, the solution is found to con- 
tain chloride of potassium and chlorate of potassa, 
which may be separated by crystallization. The 
reaction which takes place maybe thus stated; 6 
K, C0 3 , and 6CaO, HO, acted on by 6C1, pro- 
duce 5KC1; 6Ca,C0 3 , and KC10 6 , while 6Aq are 
evolved. 

429. The Salts of Phosphorus. — These salts 
are the hypophosphites, M, P 2 2 , the phosphites, M, 
P 2 4 , the monobasic phosphates, M, P 2 6 ; the bi- 
basic phosphates, M 2 , P 2 7 , M+H, P 2 7 ; and the 
tri-basic phosphates, M 3 , P 2 8 , M 2 +H, P 2 8 , M+ 
H 2 , P 2 8 . 

430. The several species of phosphates form one 
of the most remarkable and interesting groups of 
salts known to the chemist. The constitution of 
these salts has been most accurately studied in the 
case of the phosphates of soda, of which there are 
no fewer than six: namely, the monobasic phos- 
phate, or metaphosphate, Na, P 2 6 ; the two bibasic- 



204 PRINCIPLES OF CHEMISTRY. 

phosphates, or pyrophosphates, Na 2 ,P 2 7 and Na+ 
H, P 2 7 ; and the three bibasic, or common phos- 
phates, Na 3 ,P 2 8 , Na ft +H, P 2 8 and Na+H 2 , 
P 2 8 . 

431. The common phosphate of soda of the shops, 
is the tribasic phosphate, with an atom of hydrogen, 
Na 2 +H, P 2 8 It is generally called the rhombic 
phosphate, and is manufactured in large quantities. It 
is alkaline to test paper, and crystallizes in oblique, 
rhombic prisms. When this salt is mixed with ni- 
trate of silver, one equivalent of the yellow tribasic 
phosphate of silver is precipitated, and two of nitrate 
of soda, and one of free nitric acid, or rather of 
nitrate of hydrogen, remain in solution; the state- 
ment of this change being that Na 2 +H, P 2 8 and 3 

Ag,N0 6 , yield Ag 3 , P 2 8 , 2 Na,N0 6 , and H, N0 6 . 

432. By the addition of pure soda to its solution, 
this salt is converted into the triphosphate, Na 3 P 2 
8 , which crystallizes in slender prisms, having a 
strong alkaline taste. This salt throws down the 
yellow triphosphate of silver from the nitrate, three 
atoms of nitrate of soda being left in the solution, 
which is neutral. 

433. When phosphoric acid is added to the rhom- 
bic phosphate, a new salt is obtained, of which the 
formula is Na+H 2 , P 2 O g . It is very soluble, has 
an acid taste, and reddens litmus paper. With three 
equivalents of nitrate of silver, this salt yields one of 
the yellow triphosphate of silver, one of nitrate of 
soda, and two of nitrate of hydrogen, or nitric acid. 

434. By heating the rhombic phosphate to a red 
heat, it is decomposed, an atom of water is evolved, 
and a new and less soluble salt is obtained, which is 
neutral to test paper, and which is the bi-basic phos- 
phate or di~pyrophosphate ; its formula being Na 2 
P 2 7 . When an equivalent of this salt is mixed 
with two of nitrate of silver, a snow-white granular 
precipitate is formed, which is the bi-basic phosphate 



SALTS OF ARSENIC. 205 

or di-pyrophosphate of silver, and two atoms of ni- 
trate of soda remain in the neutral solution. 

435. When the tribasic phosphate, represented by 
Na+H 2 , P 2 8 , is heated to 400°, it loses one atom 
of hydrogen, and when the heat is raised above 600°, 
it loses the elements of water, and is left as a sim- 
ple pyrophosphate of soda, Na, P 2 7 . Its solution 
is neutral to test paper; it decomposes two equiva- 
lenls of nitrate of silver, precipitating the snow-white 
granular di-pyrophosphate, and leaving one atom of 
nitrate of soda and one of free nitric acid, in the 
solution. 

436. When this last salt is heated to low redness, 
it is converted into the monobasic phosphate or me- 
taphosphate of soda, which is a very soluble, deli- 
quescent, transparent glass, and reddens litmus pa- 
per. When mixed with an equivalent of nitrate of 
silver, gelatinous flakes which cohere into a soft 
mass by being heated, are precipitated. This is the 
monobasic phosphate or metaphosphate of silver. 

437. It thus appears that these acids are distinct 
species, and carry their specific differences into their 
saline combinations. On the old theory of salts, the 
differences between the above phosphates is stated 
to consist in the greater or less number of atoms of 
basic water. 

These acids form corresponding salts with the 
other bases; those of potash and lime have been 
examined. The triphosphate of lime is formed as 
a mineral in large mountain masses. 

438. The Salts of Arsenic. — These salts are the 
arsenites M, As 2 4 , the monobasic arseniates, M, 
As 2 6 , and the bibasic and the tribasic arseniates, of 
which the constitution is the same as that of the cor- 
responding phosphates. 

The arseniates may be decomposed by being 
heated to redness with charcoal, which disengages 
metallic arsenic. 

18 



206 



PRINCIPLES OF CHEMISTRY. 



The arsenic acid resembles the phosphoric acid in its 
atomic constitution, and forms an isomorphous group 
of salts. The two groups are particularly interest- 
ing, as showing the influence which a similar atomic 
constitution exercises, not only over the form of crys- 
tallization, but over the chemical affinities and pro- 
perties of bodies. Thus arsenic acid, like phospho- 
ric, has a strong tendency to combine with three 
atoms of soda, forming a tri-arseniate, and this salt 
readily passes into one, with two atoms of soda and 
one of basic water, or into one with one atom of 
soda and two of basic water, corresponding in pro- 
perties with the analogous phosphates. It also forms 
tri-arseniates, di-arseniates, and arseniates, with other 
of the metallic bases. 

439. The Salts of Chrome. — The neutral chrom- 
ates of the protoxides are isomorphous with the 
corresponding sulphates, their atomic constitution 
being the same, MO, Cr0 3 . 

The neutral chromate of potassa is of a yellow, 
and the bichromate of a ruby-red colour. The chro- 
mate of lead is an insoluble powder, of a brilliant 
yellow colour, and is much used as a pigment. The 
dichromate of lead is red, and the chromate of silver 
of a rich purple colour. 

440. The Salts of Boron. — Owing to the feeble- 
ness of its chemical energies, boric acid is separated 
from all its compounds by most of the other acids, 
and yet, owing to its being fixed in a temperature 
in which most of the other acids are volatile, it will 
decompose even the sulphates at a red heat. 

The biborate of soda is known in commerce by 
the name of borax, and is found native in certain 
parts of India; it is also prepared from the native 
boric acid of Tuscany. It turns vegetable blues 
green, and is used in the arts as a flux for promoting 
the fusion of the metals. 

441. The Salts of Silicon. — The silicates are ex- 
tensively distributed in the mineral kingdom, some 



SALTS OF SILICON. 207 

of them being the most abundant, and others the 
most beautiful of minerals. The double silicates 
especially, form a group of much interest to the 
mineralogist, from the light which they throw on 
the laws of isomorphism. 

442. The silicates of potassa and soda are the bases 
of the different varieties of glass. Silicic acid combines 
with the alkalies in various proportions, and when a 
great excess of alkali is present, the compound is 
soluble in water. A mixture of 70 parts of carbon- 
ate of potassa, 54 of dry carbonate of soda, and 152 
of fine quartz sand, forms a very soluble and fusible 
glass. 

443. The different kinds of glass can scarcely be 
regarded as definite chemical compounds, so much 
as intimate mechanical mixtures of various silicates. 
When glass is kept in a soft state for a considerable 
time, the silicates gradually separate, the mass be- 
comes opaque, almost infusible, and so hard, as to 
strike fire with steel. In this state it is called Reau- 
mur's Porcelain. 

444. The hard white glass made in Bohemia, 
which is so valuable to the chemist, consists of 70 
per cent, of silica, 15 to 18.8 of potassa and soda, 
and 10 of lime; the English plate or crown glass 
contains 63 of silica, 22 of potassa, and 15 of lime ; 
the green bottle glass of the French contains from 
53 to 60 of silica, 3 to 5 of potassa, 21 to 30 of lime, 
and 15 to 12 of alumina and iron. English plate 
glass contains 52 to 60 of silica, 14 to 9 of potassa, 
and 33 to 28 of oxide of lead. The celebrated opti- 
cal glass of Guinaud yields 42.5 of silica, 11.7 of 
potassa, and 43.5 of oxide of lead. The oxide of 
lead greatly increases the refractive power, brillian- 
cy, and fusibility of the glass. In order to deprive 
glass of the extreme brittleness which characterizes 
it when suddenly cooled, it is kept for many days in 
an oven, the heat of which is very gradually lessen- 
ed. The process is called annealing. 



208 PRINCIPLES OP CHEMISTRY. 

445. The various kinds of porcelain and earthen- 
ware are the silicates of alumina. The basis of them 
all is pure clay, which is a neutral silicate of alumi- 
na. In order to increase its fusibility, silica, lime, and 
potassa, are added, without which the clay would 
have so little coherence, and would contract so much 
in baking, as to destroy its value and beauty. The 
iron-stone china is formed of 40 parts of pure clay, 
40 of feldspar, 5 of flint glass, and 10 of fine sand. 

The various kinds of glass and porcelain are col- 
oured by means of the metallic oxides, which fuse 
into highly coloured, transparent glasses with silica. 
Glass and porcelain are coloured blue by cobalt, 
green by chrome, copper, and iron; yellow by iron 
'and silver; orange by nickel and silver; red by cop- 
per, crimson by gold, and purple by manganese* 



Section IV. 

THE SULPHUR SALTS. 

446. These salts are the double sulphurets, as the 
oxygen salts are the double oxides. The resem- 
blance of the two classes is perfect. The principal 
sulphur bases are the protosulphurets of the bases of 
the alkalies, alkaline earths, and earths; and the 
principal sulphur acids, the sulphurets of the bases 
of metallic oxygen acids, and in all these combina- 
tions, if the sulphur be replaced by oxygen, the cor- 
responding oxygen acids, bases, and salts will be 
formed. 

The most important of these salts are the sulpho- 
hydrates of potassium and sodium. They are crys- 
talline soluble salts, of an acrid bitter taste, and are 
represented by the formula KS, HS, and NaS, HS. 
They form a delicate test of the presence of metallic 
sails, especially of those of lead, by the copious dark 
precipitate which they occasion. 



PART SECOND. 



ORGANIC CHEMISTRY; OR, THE CHEMISTRY OF THE 
COMPOUND RADICALS. 



CHAPTER I. 



GENERAL VIEWS. 



447. It is impossible to frame a perfect system of 
arrangement for the facts of a science which is im- 
perfectly understood, or has been but partially ex- 
plored. The progress of knowledge consists, in truth, 
in the gradual development of the arrangement of 
physical phenomena, according to their essential re- 
lations; and those imperfect attempts at effecting 
this one great end of philosophical research, which 
subsequent discoveries have compelled us to reject 
as inadequate, are not without their use; and may 
serve as temporary lights to guide our footsteps 
along an uncertain path, until we gain the solid 
ground and clear daylight of truth. 

In no science is the force of these remarks more 
to be felt than in organic chemistry. The vast va- 
riety and complexity of substances of which it treats, 
have hitherto obliged its cultivators to submit to an 
arbitrary classification, from which we are not at 
present able to disengage the science. 

448. Among the various arrangements that have 
been proposed for this part of our subject, perhaps 
there is none more convenient than to class together 
the compounds of carbon. 



210 PRINCIPLES OF CHEMISTRY. 

There is this peculiarity in this element, that al- 
though it is itself the most tasteless, inodorous, in- 
soluble and infusible of all substances, its compounds 
are generally liquid or gaseous, or very easily fusi- 
ble solids, odorous, and readily undergoing decompo- 
sition. With hydrogen and oxygen it forms the 
basis of all vegetable, and with hydrogen, oxygen, 
and nitrogen, that of all animal structures, produ- 
cing, by the combinations and permutations of these 
few elements, the innumerable complex forms of 
organic products. 

449. The compound substances examined in the 
preceding part of this treatise, are characterized by 
the variety of the elements of which they are com- 
posed, and the simplicity of their laws of combina- 
tion. In organic chemistry, on the other hand, we 
find substances of peculiar and even opposite pro- 
perties composed of the same three elements, slightly 
differing in their proportions, and apparently baffling 
all attempts at a just classification. 

Even here, however, we may perceive the dawn 
of a clear light, which will probably enable us to 
bring these multitudinous compounds under the 
same general laws that govern inorganic matter. A 
considerable number of them have already been 
ascertained to be binary compounds, of radicals 
more or less complex, which unite in the same man- 
ner as the simple elements with other bodies, and 
are capable of separation from their combinations, 
without themselves undergoing decomposition. We 
find in this department of chemistry, as in the other, 
acids, alkalies, and salts; and we also find a large 
class of compounds, the ethers and the essential oils, 
&c, of which inorganic chemistry furnishes few if 
any examples. 

450. From a review of the various compounds 
which have passed under notice, it is evident that 
there are two great classes into which they may be 
divided; those namely, which are neutral or indif- 



ORGANIC RADICALS. 211 

ferent in their chemical relations, as the salts; and 
those which possess energetic affinities, as the acids 
and alkalies. 

451. Viewed from another point, they admit of 
being divided into two great classes; namely, one 
of binary compounds, formed by the union, atom to 
atom, of two elements; and the other consisting of 
several atoms combined into a single group, which 
acts the part of an elementary body. 

452. Sulphurous acid, S0 2 , is a compound of the 
latter class; being the sole product of the direct 
union of sulphur and oxygen. The other oxides of 
sulphur are, as has been stated, conceived to be 
compounds of sulphurous acid, and not of sulphur 
itself. Thus hyposulphurous acid is S0 2 +S, and is 
a true sulphur acid, which unites with sulphur bases 
to form sulphur salts. Hyposulphuric acid is 2S0 2 
+0; sulphuric acid is S0 2 +0; chlorosulphurous 
acid is S0 2 +C1; iodosulphurous acid S0 2 +I; and 
nitrosulphurous acid S0 2 +N0 2 . By this mode of 
conceiving the nature of these bodies, we reconcile 
many seeming anomalies, and explain many phe- 
nomena not intelligible on the old view. 

453. Organic Radicals, — There are numerous 
cases in which we are compelled to resort to similar 
suppositions respecting the constitution of compound 
bodies, in order to arrive at clear notions of the 
changes which they undergo, by the operation of 
chemical forces. There are, for example, several 
organic products which combine, amidst various 
changes of composition, with one or more atoms of 
most of the simple elements. When these various 
compounds are analyzed, the chemist perceives that 
there is a certain combination of atoms common to 
them all; and that if there were a substance so con- 
stituted, all the changes he has observed could readily 
be explained as so many combinations of that com- 
plex radical. Even if this substance cannot be sepa- 



212 PRINCIPLES OF CHEMISTRY. 

rated from its combinations and exhibited/?^ se, the 
chemist has no hesitation in admitting its existence, 
and allowing it a place and a name in the list of 
organic elements. 

454. Such an hypothetical radical is benzule. The 
essential oil of bitter almonds has long been a sub- 
ject of interest and research to the chemist, on ac- 
count of the powerful poison which it contains. 
Another organic product which has been subjected 
to frequent and accurate analysis, is the volatile acid 
obtained from gum benzoin. These substances 
have been subjected to the action of powerful re- 
agents, and made to enter into combination with the 
simple elements. The result has been the full proof 
of the existence of the complex radical benzule, re- 
presented by C 14 H 5 2 , although it has never yet 
been insulated. The protoxide of this substance is 
benzoic acid: with an atom of hydrogen it forms 
the oil of bitter almonds; and it enters into combi- 
nation with chlorine, bromine, iodine, and sulphur, 
besides forming a great variety of other compounds 
with organic bodies. 

455. It is evident that in these cases, the atoms 
which constitute benzule are held together by a 
stronger affinity than unites that radical to its seve- 
ral compounds, for it remains unchanged amidst a 
series of decompositions and recompositions. 

456. The discovery of numerous radicals of this 
kind has entirely changed the state of this depart- 
ment of chemistry, and thrown a clear and steady 
light upon some of its obscurest portions. 

These compound radicals belong to all the various 
classes which have been found to exist among the 
simple elements in inorganic chemistry. Cyanogen, 
NC 2 ,is a genuine salt radical, belonging to the same 
class as chlorine and bromine; ethule, H 5 C 4 , may be 
regarded as a compound metal, for it forms a series 
of basic oxides, which neutralize acids, and benzule 



ATOMIC CONSTITUTION. 



213 



belongs to the group which contains the electro-nega- 
tive elements, among which are the bases of the 
principal acids. 

457. Dependence of Chemical Properties upon 
similarity of Atomic Constitution. — The search- 
ing analysis to which these bodies have been sub- 
jected, has proved new and most remarkable laws 
to govern their composition. The radical ethule, for 
example, passes unchanged into combination with a 
vast variety of substances, without having yet been 
insulated. At a red heat, oxygen will entirely de- 
compose it, as it does all other organic products, 
converting it into water and carbonic acid. So, 
likewise, by the action of heat alone, almost all 
organic products can be separated into new or sim- 
pler combinations of their elements. These organic 
radicals are also capable of a partial decomposition 
which has peculiar laws. They may be regarded 
as groups of atoms, having a certain physical or 
mechanical structure, which appears to exercise 
some influence upon their affinities, and to resist 
decomposition, or to modify the action of reagents. 

458. Thus, there is a radical called acetule, C 4 H 3 , 
which forms a series of compounds with the simple 
elements; its hydrated oxide, C 4 H 3 , O+Aq, is the 
liquid called aldehyde, and its hydrated teroxide 
C 4 H 3 ,0 3 + Aq, is acetic acid. Under certain cir- 
cumstances, the radical itself is decomposed by chlo- 
rine, with the complete substitution of chlorine for 
hydrogen, so that a new radical, C 4 C1 3 , is obtained, 
which forms a series of combinations, parallel with 
those of acetule, and possessed of very analogous 
properties. Thus its terhydrated oxide is the chlora- 
cetic acid, C 4 Cl 3 3 +Aq, which forms a series of salts 
parallel with the acetates,and preserving throughout, 
the analogy of characters which has been mentioned. 

459. So likewise a series of organic compounds 
has been discovered, of which alcohol may be re- 



214 ORGANIC CHEMISTRY. 

garded as the type. They all agree in their general 
chemical characters; they all contain carbon, and 
hydrogen in their atomic proportions, and combined 
with two atoms of water; the abstraction of an atom 
of water, converts them all into substances having 
the generic qualities of ether, and by the substitution 
of two atoms of oxygen for the Hydrogen of their 
water, they are all converted into acids. 

Alcohol. Ether. Acid. 

Wine alcohol, 

C 4 H 4 +2Aq, C 4 H 4+ Aq, C 4 H 4 +0 4 . 
Wood alcohol, 

C 2 H 2 +2Aq, C 2 H 2 +Aq, C 2 H 2 +0 4 . 
Oil of potato spirits, 

C 10 H 10 +2Aq, C 10 H 10 +Aq, C 10 H 10 +0 4 . 
Ethal, 

C 32 H 32+2Aq, C 32 H 32 +Aq, C 32 H 32 +0 4 . 
460. Upon a closer examination it will be found 
that these changes and substitutions are in perfect 
harmony with the laws of inorganic chemistry. De- 
composition destroys nothing, it merely changes. 
An element leaves the combination in which it exists, 
for a new one, because it is solicited by a more 
powerful affinity; and if in any case it is disengaged 
in its elementary form, it is because the associated 
atoms have been drawn away by a stronger attrac- 
tion than its own, or because its own repulsion of 
elasticity, or attraction of cohesion, is stronger than 
its affinity for any of the elements, or combinations, 
that are present. 

When a bi-eleme.ntary compound is decomposed, 
one of the elements is almost always set free, and 
in proportion to its complexity of constitution, do the 
elements of a body, instead of being separately evolv- 
ed, reunite into new combinations. 

We can readily understand why it is, that water 
and carbonic acid are the most constant products of 
vegetable ; and water, carbonic acid, and ammonia, of 



LAW OF SUBSTITUTION. 215 

animal decompositions; for they are the most stable 
compounds, which the respective elements are capa- 
ble of forming with each other, and they are always 
produced when the elementary affinities have full 
play. 

461. Law of Substitution. — The partial decom- 
position moreover, which these complex organic pro- 
ducts frequently undergo, and which changes the 
character, but not the number, nor probably the 
arrangement of the atoms, by substituting an equi- 
valent of another kind for the one which is removed, 
is an exemplification of the same law. 

462. When acetule is subjected to the action of 
chlorine, six atoms of chlorine are engaged in the 
decomposition of a single atom of acetule. Three of 
these unite with the three atoms of hydrogen, which 
are displaced, and form chlorohydric acid, which is 
disengaged, while the other three replace the hydro- 
gen which is removed. 

Frequently there is a partial displacement by 
which a new radical is formed, which combines in 
its nascent state with other elements. Thus alco- 
hol is the hydrated oxide of ethule, C 4 H 5 , O+HO. 
When it undergoes the acetous fermentation it ab- 
sorbs four atoms of oxygen from the air; two of them 
combine with two atoms of its hydrogen to form 
water, thus converting the ethule, C 4 H 5 , into a 
new radical, acetule, C 4 H 3 , which seizes in its nas- 
cent state upon the other two atoms of oxygen, 
to form acetic acid, which is a teroxide of acetule, 
C 4 H 3 , 3? and which retains the atom of water, 
originally contained in the alcohol, as it is incapable 
of existing except in combination with a base. So, 
likewise, when equal weights of acetate of potassa, 
and arsenious acid, are exposed to a dull red heat, a 
dense fuming liquid is obtained, which is the oxide 
of a new complex radical. This radical, which has 
received the barbarous name of Kakodule, is pro- 



216 PRINCIPLES OF CHEMISTRY. 

duced by the breaking up of the acetic acid, and is 
remarkable for containing metallic arsenic. Its for- 
mula is C 4 H 6 As. It unites with the electro-nega- 
tive elements, forms an acid and a salifiable base, 
and is distinguished from every other series of the 
kind, by the insupportable odour and deadly poison 
of all its compounds. 

463. The impossibility under which many of these 
organic products labour of separate existence, is a 
frequent cause of their decomposition. When a sub- 
stance is presented to them which abstracts the base 
with which they are combined, they are decom- 
posed in the act of separation into simpler and more 
permanent combinations. Thus oxalic acid, C 3 3 , 
cannot be obtained in a purer form than its sesqui- 
hydrate; and when its crystals are heated with sul- 
phuric acid, the water is abstracted, and the oxalic 
acid separates into carbonic oxide, CO, and carbonic 
acid, C0 2 . 

464. When these organic products are subjected 
to the action of highly oxygenated bodies, such as 
nitric or chloric acid, or the peroxide of lead, or 
manganese, they always combine with the oxygen, 
and are reduced to simpler forms containing fewer 
atoms. 

The oxygen, according as the action is more or 
less intense, converts more or less of the hydrogen 
into water, sometimes replacing a portion of that 
which it abstracts, and sometimes combining directly 
with the body itself. Thus when gum, C 12 H 10 O 10 , 
is subjected to the action of nitric acid, it first con- 
verts two atoms of the acid into deutoxide, and seiz- 
ing upon the disengaged oxygen, is converted into 
mucic acid, C 12 H 10 O 16 . By increasing the heat, 
an additional portion of nitric acid is decomposed, 
all the hydrogen is converted into water, two addi- 
tional atoms of oxygen enter into combination; and 



ORGANIC PRODUCTS. 217 

the mucic acid is converted into six atoms of oxalic 
acid,6C 2 3 =C 12 18 . 

465. In other cases both bodies are decomposed 
or changed, and the resulting compounds combine to 
form a new product. Thus when defiant gas, C 4 H 4 , 
is subjected to the action of chlorine, an oily liquid 
is formed, which contains C,ELCL . In this case the 
chlorine replaces an atom of hydrogen, which it con- 
verts into chlorohydric acid, and the two products 
combine, so that the true formula of the oily liquid is 
C 4 H 3 , C1+HC1. So, likewise, when nitric acid acts 
on the substance called naphthaline, the composition 
of which is C 20 H 8 ,itis decomposed into nitrous acid 
and oxygen; the latter abstracts an atom of hydro- 
gen, which is replaced in the compound by the atom 
of nitrous acid, and the product is C 20 H 7 +N0 4 . At 
the same time another atom of naphthaline is divided 
into two, each containing C 10 H 4 , and the same 
change takes place in this new atom as in the old; 
a portion of the naphthaline being resolved into the 
new product, C 10 H 3 +N0 4 . 

466. Spontaneous changes in Organic Products. 
— The stability, equally with the chemical energy of 
these organic products, varies greatly. Mere ex- 
posure to warm and moist air is in a large number 
of cases sufficient to induce decomposition. Those 
bodies which are most liable to this spontaneous 
change are the immediate constituents of vegetables, 
and animals, such as sap, blood, milk, and animal 
and vegetable fibres. When the vital principle, 
which is capable of preserving these for a long course 
of years, departs, the change at once begins. So 
slight are the affinities which hold them together, that 
the tendency of their elements to enter into simpler 
combinations soon developes itself; the hydrogen 
and nitrogen form ammonia; and the carbon and 
hydrogen seize upon the oxygen of the air, and 
form carbonic acid and water. A variety of fetid 

19 



218 



PRINCIPLES OF CHEMISTRY. 



gases, due to the presence of sulphur, phosphorus, 
&c, are disengaged, and the whole mass soon be- 
comes putrid. 

467. This putrefaction does not take place if the 
heat is sufficient to coagulate the albuminous fluids 
and to drive off the water, nor when the latter is 
congealed by cold. It is prevented also by the pre- 
sence of salt, or of alcohol, which abstracts the wa- 
ter, and of reagents, such as corrosive sublimate, 
&c., which combine with the organic tissue, and ren- 
der its affinities more stable. 

468. This spontaneous change, which takes place 
rapidly under favourable circumstances, may be 
greatly prolonged by moderating its activity. It 
then becomes, in fact, a slow combustion, in which 
only the more combustible element is slowly con- 
sumed. Such is the mouldering decay which wood 
undergoes, in which the greater part of the hydro- 
gen, and a portion of the carbon, are burnt out, while 
the organic texture is destroyed, and a pulverulent 
carbonaceous mass remains — the vegetable mould or 
humus, so fertilizing to the soil. 

469. Starch, Gum, Sugar. — The most abundant 
products of vegetable secretion, are starch, gum, and 
sugar. Their composition is nearly the same, being 
twelve atoms of carbon united with varying quan- 
tities of oxygen and hydrogen in their atomic pro- 
portions. Thus the composition of starch, and of 
gum, is C x 2 H 10 O 1 , of sugar from the sugar cane, 
C i2 H ii°n> or C 12 H 10 O 10 +Aq, and of sugar 
from grapes, C 12 H 12 12 , or C 12 H 10 O 10 +2Aq. 
The forces which hold these atoms together, are so 
nearly balanced by the divellent affinities, that slight 
causes are sufficient to effect their transformation 
into new compounds, and the conversion of all the 
others into sugar of grapes. 

470. Ferments. — The transformation which grape 
sugar itself, in certain circumstances, undergoes, is 



FERMENTS. 219 

one of the most remarkable phenomena in chemis- 
try. When the air is entirely excluded, its solution 
remains without change; but with the free access 
of the air, it obeys the ordinary law of organic de- 
cay, loses its sweetness, and becomes discoloured, 
sour, and fetid. There is a substance well known 
by the name of yeast ox ferment, which is the scum 
that collects on the surface of fermenting beer. Let 
a small portion of yeast be added to the solution of 
sugar, kept at a temperature of 70° or 80° in a close 
glass vessel, and let a tube pass from the vessel to a 
pneumatic apparatus containing mercury, so that all 
the gaseous products can be collected. In a short 
time the mixture becomes turbid; minute bubbles of 
gas begin to collect ; the temperature and the inter- 
nal agitation increase, and then gradually subside, 
and the solution again becomes cool and clear. 

471. If we now examine the products, we shall 
find that a quantity of carbonic acid gas has been 
collected over the mercury, and that the liquid has 
lost all the properties of sugar, and is converted into 
a new substance, alcohol. The change which has 
thus taken place, is a mere transformation of the 
elements of the sugar. Grape sugar consists of C 12 
H 12 12 , alcohol of C 4 H 6 2 , and carbonic acid 
of C 2 ; so that each atom of sugar has been con- 
verted into two of alcohol and four of carbonic acid. 

472. Although nothing has been either gained or 
lost in this process, the presence of ferment is essen- 
tial to the change. What then is the nature of its 
agency? 

Yeast consists chiefly of gluten — a vegetable prin- 
ciple containing much nitrogen; and it is efficacious 
as a ferment only when it is itself in an active state 
of decomposition. The internal agitation of its par- 
ticles is then sufficient, when it is diffused through- 
out the saccharine liquid, to overcome the vis-inertise 
of the forces by which the elements are held to- 



220 PRINCIPLES OP CHEMISTRY. 

gether as sugar, and to induce new arrangements by 
which stronger affinities come into play. This mo- 
lecular agitation is propagated from the yeast to the 
adjoining particles of sugar, and from these, particle 
by particle, throughout the whole mass, till the de- 
composition is complete. 

473. This force,, by means of which the presence 
of one body brings about, in the chemical arrange- 
ments of another, a change altogether disproportion- 
ed to the relative quantities and ordinary reaction of 
the bodies, has received the name of catalysis, and 
has been supposed, without sufficient foundation, to 
be a new and anomalous power. In the present 
case, the principle on which the change takes place, 
is precisely like that which governs the cases before 
noticed, in which a decomposition, begun in a single 
particle, is propagated throughout the whole mass, 
by the disturbance of the equilibrium of forces which 
had maintained the atoms of the compound in a 
quiescent state. 

474. This power, which bodies in a state of de- 
composition possess, of inducing the same state in 
those with which they come in contact, is the cause 
of many of the transformations which occur among 
organic products. 



CHAPTER II. 

THE COMPOUNDS OF CARBON WITH ELECTRO-NEGATIVE 
ELEMENTS. 

Section I. 

CARBON AND OXYGEN. 

475. Carbonic Oxide. CO; 6.12+8=14.12. This 
oxide may be prepared by heating to a red heat in 
a gun-barrel, a mixture of two parts of well dried 



OXALIC ACID. 221 

chalk (carbonate of lime) and one part of pure iron 
filings. The gas which is evolved must be collected 
over water, and will be found to be a mixture of 
carbonic acid and carbonic oxide. The former is 
readily absorbed by the water, leaving the latter 
pure. Carbonic oxide may also be prepared by 
heating in a glass retort, one part of binoxalate of 
potassa, oxalate of ammonia, or oxalic acid itself, 
with five or six times its weight of sulphuric acid. 
In the former process the iron is oxidated by the 
abstraction of an atom of oxygen from the carbonic 
acid which is thus resolved into carbonic oxide. The 
carbonic acid gas which comes over is evolved by 
the decomposition of the carbonate of lime. In the 
latter case the oxalic acid is resolved into carbonic 
acid and carbonic oxide, by the action of the sul- 
phuric acid. 

Carbonic oxide is a colourless, tasteless, inflam- 
mable gas, which is sparingly absorbed by water, 
and has no action on earths or alkalies. 

When a lighted taper is plunged into a jar full of 
this gas, the taper is extinguished after setting fire 
to the gas, which burns quietly with a pale blue 
flame. Carbonic oxide gas is highly deleterious to 
the animal system; taken into the lungs it occasions 
headache, and when breathed pure, almost instantly 
produces stupor. 

The specific gravity of carbonic oxide gas is .9727. 
A mixture of 100 measures of this gas and 50 mea- 
sures of oxygen explodes by the electric spark, and 
is converted into 100 measures of carbonic acid. 

476. Oxalic Acid. C 2 3 ; 12.24+24-36.24. This 
acid is evolved in the process of vegetation, and 
exists in combination with potassa, in the rumex 
acetosa, and the oxalis acetosella, or sorrel, from 
which last plant it has derived its name. It also 
exists in combination with lime in several species of 
lichen. Oxalic acid may be prepared artificially by 

19* 



222 PRINCIPLES OF CHEMISTRY. 

digesting sugar in five or six times its weight of 
nitric acid, and distilling off the excess of acid; the 
residue, on cooling, yields crystals of oxalic acid 
which amount to about one half the weight of the 
sugar. The acid may be prepared from many other 
organic substances, as gum, starch, wool, hair, and 
silk. 

Oxalic acid has a very sour taste, reddens vege- 
table blues, and forms neutral salts. It crystallizes 
in slender flattened four or six sided prisms, with 
di-hedral summits, the primary form of which is an 
oblique rhombic prism. These crystals are a com- 
pound of one atom of acid, and three atoms of water, 
two of which escape when they are heated to 212°; 
they are permanent at common temperatures, but 
effloresce in a higher temperature, fuse in their own 
water of crystallization at 209°, and dissolve in 15.5 
times their weight of water at 50°. They are also 
soluble in alcohol. Oxalic acid evaporates very 
slowly at common temperatures, and when heated 
to 330° it sublimes rapidly and condenses in trans- 
parent acicular crystals, which contain one atom of 
water. 

Oxalic acid is a rapid and fatal poison, the proper 
antidote for which is a mixture of chalk and water. 

Oxalic acid may be distinguished from all other 
acids by its form of crystallization, and by its form- 
ing with lime a white precipitate insoluble in an ex- 
cess of acid. ^~ 

477. Carbonic Acid. C0 2 ; 6.12+16=22.12.— 
Carbonic acid may be prepared by decomposing 
fragments of marble, (carbonate of lime,) with dilu- 
ted chlorohydric acid, and collecting the gas over 
mercury. Carbonic acid is an invisible inodorous 
gas, which is condensed beneath a pressure of 36 
atmospheres into a transparent colourless fluid. 
This fluid is the most expansible body known; at 
32° its sp. gr. is .83, and its expansion is nearly 



CARBONIC ACID. 223 

one per cent for each degree of Fahrenheit, which 
is four times that of air. If a jet of the liquid 
acid be directed into a small cylindrical vessel, the 
cold produced by the sudden conversion of one part 
into gas, will be sufficient to congeal the remainder 
into a soft snow-like mass, which evaporates very 
slowly. 

478. Carbonic acid gas is incombustible; it ex- 
tinguishes all burning bodies except potassium, and 
destroys animal life when it forms only a fourth part 
of the atmosphere. When an attempt is made to 
breathe carbonic acid it causes a violent spasm of 
the glottis which prevents the air from entering the 
lungs. If the gas be so much diluted with common 
air that it can be breathed, it acts as a narcotic poi- 
son and proves speedily fatal to life. Its sp. gr. is 
1.524. 

479. The liquid differs from the gaseous carbonic 
acid in a very remarkable circumstance. The 
former mingles in all proportions with ether and 
alcohol, but not with water, on the surface of which 
it floats like oil. On the other hand carbonic acid 
gas is readily diffused through water, which will 
take up its own bulk at the common atmospheric 
pressure. The quantity of the air compressed into 
the water is in exact proportion to the pressure, and 
the gas escapes as soon as that pressure is removed. 
These phenomena closely resemble those caused by 
the mutual indifference and penetration of the gases. 
Carbonic acid and water are mutually indifferent, 
and the presence of the latter, like that of a gas, is 
no obstacle to the diffusion throughout its mass and 
between its particles, of the former. When both 
materials are in a liquid state, the attraction of grav- 
itation separates them, and the lighter fluid floats 
above the heavier. 

480. The artificial Seltzer waters sold in the 



224 PRINCIPLES OF CHEMISTRY. 

shops, are prepared by forcing into a strong metallic 
vessel, containing water, six or eight times its volume 
of carbonic acid gas. The effervescence of these 
waters, and their pleasant acidulous taste, are owing 
to the presence and escape of the acid. It is to the 
presence of the same acid, evolved during the vinous 
fermentation, that beer, cider, and sparkling wines, 
owe their agreeable pungency. 

Water, holding carbonic acid in solution, reddens 
litmus paper; the acid is expelled by boiling, or by 
removing the atmospheric pressure. Carbonic acid 
may be distinguished from other acids by forming a 
precipitate with lime water, which effervesces when 
mixed with any other acid. 

Carbonic acid is extensively diffused throughout 
nature. It always exists in the atmosphere, and in 
natural waters; it is evolved in the process of respi- 
ration, vegetation, and fermentation; it is discharged 
in great quantities from fissures in the earth, and 
from springs of water in certain volcanic regions; 
and in combination with lime and other metallic 
oxides, it forms a large portion of the earthy and 
rocky crust of the globe. 

481. The Carbonates. — The carbonates are de- 
composed with effervescence by nearly all the acids. 
Most of them part with their acid when heated to 
dull redness; the carbonates of lime and magnesia 
are decomposed at a full red heat, those of baryta 
and strontia at an intense white heat, and those of 
potassa, soda, and lithia, are unalterable in the fire. 
When the carbonate of lime is subjected to an in- 
tense heat, under a very great pressure, it fuses, 
without decomposition, into a crystalline mass. Ex- 
cepting those of the alkalies, the carbonates are 
sparingly soluble in water. 

482. The carbonate of potassa is procured from 
the ashes of vegetables by lixiviation and evapora- 



THE CARBONATES. 225 

tion, and is known by the names of potash and 
pearlash. In this state it always contains other 
salts, chiefly the sulphate of potassa and chloride of 
potassium. A pure carbonate of potassa is obtained 
by heating the bitartrate of potassa to redness. A 
mixture of charcoal and pure carbonate is left, from 
which the latter may readily be obtained by solution 
in water. It may thus be obtained in crystalline 
grains, and in this state it is called salt of tartar. 

Pure carbonate of potassa has a strong alkaline 
taste, turns vegetable blues green, and is slightly 
caustic. It is highly deliquescent, dissolves in less 
than its weight of water at 60°, and crystallizes with 
difficulty from its solution. It fuses at a full red 
heat, and is insoluble in alcohol. Its principal uses 
in the arts are in the manufacture of soap and glass. 

When a current of carbonic acid gas is passed 
through a solution of the carbonate of potassa, a 
bicarbonate is formed, which crystallizes in octohe- 
dral prisms, requires four times its weight of water 
at 60° to dissolve it, and does not deliquesce. 

483. The carbonate of soda is obtained by lixiv- 
iating the ashes of sea weeds, and when thus made 
is called kelp and barilla. It is also prepared by 
decomposing the sulphate of soda at a red heat by a 
mixture of sawdust and lime. Sulphuret of calcium 
and carbonate of soda are formed, and the latter is 
obtained by lixiviation and crystallization. Carbo- 
nate of soda has an alkaline taste, and turns vege- 
table blues green; it crystallizes in octohedrons with 
a rhombic base, containing either 7 or 10 atoms of 
water. Its crystals effloresce in the air; when heated 
they fuse in their own water of crystallization, and 
dissolve in about two parts of cold water. 

484. A sesquicarbonate of soda is found native in 
central Africa, being contained in the waters of cer- 
tain lakes which become dry in summer. It is called 



226 PRINCIPLES OP CHEMISTRY. 

trona, whence one of the names of soda, natron, is 
derived. 

By passing carbonic acid gas through its solution, 
the carbonate is converted into a bicarbonate, a less 
soluble and less alkaline salt. 

The carbonate of lime is one of the most abundant 
salts in nature. Chalk, marble, limestone, are car- 
bonates of lime; and it is the principal material of 
the shells of molluscous animals. The form of its 
primitive crystal is a rhomboid, and the number of 
its secondary forms exceeds two hundred. 

The protocarbonate of lead is the common pig- 
ment called white lead. 

The bicarbonate of lime and magnesia is a native 
crystalline limestone rock, known by the name of 
dolomite. 

485. Carbon forms three other acids with oxygen, 
the rhodizonic, which is a tribasic acid, its composi- 
tion being C 7 7 +3Aq, or C T O 10 +H 3 ; the croconic 
acid, C 5 4 +Aq, or C 5 5 +H; and the mellitic acid, 
C 4 3 +Aq, or C 4 4 +H. It is highly probable that 
carbonic oxide is the real base of all these com- 
pounds. In this case oxalic acid will be represented 
by 2CO+0, and carbonic acid by CO+O. 

Carbonic oxide also unites as a base with chlorine 
to form what is called the chlorocarbonic acid, 
CO+C1, the phosgene gas of Davy. 



Section II. 

CARBON AND THE SALT RADICALS. 

486. The chloride, bromide, and iodide of carbon, 
are volatile, aromatic, crystalline solids, or transpa- 
rent liquids, analogous to camphor and the essential 
oils in their properties. 



COMPOUNDS OF CARBON AND HYDROGEN. 227 



Section III. 

CARBON AND SULPHUR. 

487. Sulphocarbonic Acid, Bisulphuret of Car- 
bon.— G S 2 ; 6.12+32.2=38.32. This acid may- 
be prepared by passing the vapour of sulphur over 
fragments of red-hot charcoal, in a porcelain tube, 
and collecting the vapour under water. It is a trans- 
parent, colourless liquid, remarkable for its high re- 
fractive power. Its sp. gr. is 1.272; it has an acid, 
pungent, slightly aromatic taste, and a highly fetid 
smell, resembling that of putrid cabbages. It is 
very volatile, boils at 110°, and produces intense cold 
during its evaporation. It is very inflammable, and 
burns with a pale blue flame. It is soluble in alco- 
hol and ether, and dissolves sulphur, phosphorus, 
and iodine, forming a beautiful pink solution with 
the latter. 

488. This acid forms true sulphur salts with the 
metallic protosulphurets; and their composition is 
such, that if the sulphur be replaced by oxygen, the 
corresponding carbonates will be formed. 



CHAPTER III. 

THE NON-NITROGENOUS COMPOUNDS OF CARBON AND 
HYDROGEN. 

489. We shall gain a clearer view of the subject 
of organic chemistry, by tracing its products from 
their more complex to their simpler forms, as we 
shall thus follow the progress of discovery, and throw 
into natural groups a variety of compounds, of which 
the theoretical relations are not well understood. 



228 PRINCIPLES OP CHEMISTRY. 

The organic radicals are conveniently divided into 
two classes, the nitrogenous and non-nitrogenous — 
the latter embracing most vegetable, and the former 
most animal products. The only ones which contain 
no carbon are amide, and its derivatives. 



Section I. 

THE ALCOHOLIC SERIES. 

490. Starch, Lignine, Gum, and Sugar. — These 
substances are the most important and abundant 
vegetable secretions. They are formed in all plants, 
and may be regarded as the stores laid apart by the 
plant itself for its own future nutriment. They are 
classed together on account of their close resem- 
blance in constitution and properties, being all formed 
of twelve atoms of carbon, combined with oxygen 
and hydrogen in the proportions to form water; and 
being easily convertible into the same product. 

491. Starch and lignine possess an organic struc- 
ture, which they retain until decomposed. Starch 
is imbedded in the cellular tissue of plants, as small 
white grains of an irregular form. Each grain con- 
sists of concentric layers, the outer ones of which 
are the most hard and insoluble, so that when the 
grain is crushed, it becomes a soft mass. It is readily 
procured from plants which contain it, by reducing 
them to a powder, and washing away the soluble 
parts with cold water. The fecula subsides in the 
form of a white powder. It is insipid, inodorous, 
and insoluble in alcohol, ether, and cold water. 
When, however, the grains of fecula are triturated 
in a mortar, so as to bruise and break the outer 
covering, the inner portion, which is soluble, being 
exposed, a partial solution in cold water may be 
effected. Boiling water readily dissolves fecula, con- 



THE ALCOHOLIC SERIES. 229 

verting it into a tenacious, bulky jelly, which forms 
when dry a solid of a horn-like transparency, which 
retains its solubility in cold water. 

Starch, like sugar, forms definite soluble com- 
pounds with the alkalies, and insoluble ones with 
the alkaline earths and oxide of lead. It is decom- 
posed by the action of sulphuric and nitric acid, 
being converted by the latter into oxalic and malic 
acids. The most delicate test of the presence of 
starch is iodine, which colours its solution blue. 

When heated a little above 212°, fecula acquires 
a slightly red tint, the odour of burnt bread, and be- 
comes soluble in cold water. The term amidine is 
applied to starch which has, either thus, or by being 
dissolved in hot water, been rendered soluble in cold 
water. 

When starch is heated still higher it assumes a 
dark colour, swells and softens, and becomes very 
similar to gum in its properties. In this state it is 
employed by calico printers, under the name of 
British gum. 

492. Fecula is readily converted into sugar. This 
change takes place in the germination of seeds, and 
may be effected by frost and by the action of dilute 
sulphuric acid. If starch is boiled for a considerable 
time in water, acidulated with --^th of its weight of 
sulphuric acid, it is wholly converted into sugar, 
identical with the sugar of grapes. 100 parts of 
starch yield 110 of sugar, and the only difference in 
their composition is, that sugar contains a greater 
proportion of the elements of water. The agency of 
sulphuric acid in effecting this change appears to 
consist in furnishing the required water; for it does 
not itself suffer any diminution in the process. 

The composition of fecula, or starch, is C 12 H 10 

o 10 - 

493. A variety of starch called Inuline, is obtained 
in the same manner as common starch from the roots 

20 



230 PRINCIPLES OF CHEMISTRY. 

of the Elecampane, Dahlia, &c. Its solution in hot 
water does not gelatinize as it cools, but deposites 
its inuline unchanged. Another variety is found in 
the Iceland moss, which is soluble in cold water. 
Their composition is the same as common starch. 

494. Lignine, or woody fibre, constitutes the 
fibrous structure of vegetable substances, and is the 
most abundant principle in plants. It is prepared by 
digesting sawdust in alcohol, water, and dilute chlo- 
rohydric acid, until it ceases to yield any soluble 
matter to these menstrua. 

Lignine has neither taste nor odour, is unalterable 
in the air, and is insoluble in alcohol, water, and the 
dilute acids. By the action of strong sulphuric acid, 
it is converted into gum, which is again changed by 
long boiling into a saccharine substance, identical 
with sugar of grapes. 

Lignine has a strong affinity for alumina, oxide 
of iron, and of tin, and will separate them from 
their combinations. When precipitated upon the 
vegetable fibre, these compounds can be combined 
with various colouring matters, which may thus 
be fixed permanently on the fibre. When paper, 
which is pure lignine, is immersed in strong nitric 
acid, and immediately well washed, it becomes thick 
and tough like parchment, and so combustible as 
to serve for tinder. The composition of lignine is 

C 12 H 8 8- 

495. Gum is a concrete juice, which exudes prin- 
cipally from the bark of many trees, and also from 
other parts of the plant. 

Pure gum is colourless, transparent, inodorous, 
insipid, brittle, and breaks with a vitreous fracture. 
It has a strong affinity for water, and forms in that 
liquid a clammy, adhesive solution. It is insoluble 
in ether and alcohol, and is precipitated by the for- 
mer from its solution in opaque white flakes. Its 
solubility is increased by acids and alkalies, and it is 



THE ALCOHOLIC SERIES. 231 

converted, when heated with strong nitric acid, into 
a peculiar acid, called the mucic acid. Gum forms 
definite insoluble compounds with several of the 
metallic oxides, especially that of lead. The solution 
of the dinacetate of lead is therefore the most deli- 
cate test of the presence of gum. 

The purest specimen of gum is gum-arabic, the 
concrete juice of the mimosa, an African tree. It is 
soluble in cold water; and the name of Arabine has 
been proposed for this species. Another species of 
gum exudes from the bark of the cherry, peach, and 
apricot. It is insoluble in cold water, but soluble in 
boiling water, and is identical in composition with 
arabine. It is distinguished by the name of Cera- 
sine. A third species, Bassora gum, is called Basso- 
vine; it swells into a jelly in hot water, but does not 
dissolve. The mucilage of flaxseed, and that from 
the bark of the slippery-elm, appear to form another 
species or variety of gum. Gum tragacanth is a 
combination of arabine and bassorine. 

The composition of gum is C 12 H 10 O 10 . 

496. Cane Sugar. — Cane sugar exists abundantly 
in the sap of certain vegetables, more especially in 
that of the sugar cane, the sugar maple, and the root 
of the beet, from all which it is extensively manufac- 
tured. 

Pure sugar is white, hard, brittle, inodorous, and 
intensely sweet. Its sp. gr. is 1.6, and it fuses at 
350° into a clear yellow liquid. It crystallizes in 
four or six sided prisms, which are bevelled on their 
edges. It is soluble in its own weight of cold, and 
to almost any extent in hot water, and in four times 
its weight of boiling alcohol. It forms definite crys- 
talline soluble compounds with alkalies and alkaline 
earths and common salt, and an insoluble one with 
oxide of lead, thus acting the part of a feeble acid. 

497. Sugar is inflammable, and is much altered 
by exposure to heat, acquiring a dark colour and an 



232 PRINCIPLES OF CHEMISTRY. 

empyreumatic taste. It is then called caramel. The 
composition of cane sugar is C 12 H 11 11 . Strong 
nitric acid converts it into oxalic acid; by the ac- 
tion of dilute nitric acid, it is converted into a pen- 
tebasic acid — the saccharic acid, the crystals of which 
consist of C 12 H 5 O l:l +5HO,and its constitution must 
be regarded as C 12 H 5 16 +H 5 . 

498. Glucose — Sugar of Grapes.— This species 
of sugar is the saccharine principle of grapes, and of 
most sweet fruits. It is also copiously secreted in 
certain diseases, such as diabetes, and is formed from 
starch in the process of germination, and from all 
the preceding compounds by artificial processes. It 
crystallizes in cubes, or in flat quadrangular tables, 
or in minute needles. Its sp. gr. is 1.3S, and it is less 
sweet and soluble than cane sugar. It is converted 
into caramel by heat, and forms definite compounds 
with metallic oxides. Its composition when crystal- 
lized is CjaH^O^+SAq, and when fused at 212°, 
Ci 3 H 11 11 +Aq, or C 12 H 12 12 . As the above 
compounds differ from each other only in the quan- 
tity of the elements of water, we can readily under- 
stand the ease with which they are converted into 
sugar of grapes. 

499. Lignine is converted into grape sugar by 
macerating in the cold, 12 parts of linen or paper 
shreds, with 5 of oil of vitriol, and one of water. 
After 24 hours the mass is dissolved in a large quan- 
tity of water, and boiled for ten hours. It is then 
neutralized with chalk, and evaporated. 

500. Starch is converted into grape sugar by moist- 
ening its paste with a solution of pale malt, and 
keeping the mixture at 160° or 170° for several hours. 
Six parts of malt will produce 2.5 of sugar. This 
change is effected by the action of a peculiar fer- 
ment, namely, the substance called diastase, which 
is formed in barley in the process of malting, and 
which can be obtained from it in the form of a gum- 



ALCOHOL. 233 

my, tasteless, white mass. It acts only when in a 
state of active decomposition, and disturbs the equi- 
librium, so as to induce a new arrangement of the 
particles of the starch. One part of diastase is suf- 
ficient to convert in a few hours 2000 parts of starch 
into sugar, if the temperature do not exceed 16S°. 

This change is also effected by boiling one part of 
starch with four parts of water, and T ^-th of sul- 
phuric acid, during 36 or 40 hours; taking care to 
renew the water as it evaporates. It is not easy to 
point out the manner in which the sulphuric acid 
acts; but the change is evidently due to the fixation 
in the gum and cane sugar of one atom, in starch of 
two, and in lignine of four additional atoms of water. 

501. Before being converted into grape sugar, 
starch is converted into a species of gum called dex- 
trine, which is isomeric with itself, and which is 
speedily changed into sugar. 

502. The Vinous Fermentation. — The changes 
which take place in the solution of grape sugar 
when it undergoes the vinous fermentation, have 
already been detailed. There is reason to believe 
that it is the only substance capable of that change, 
and that cane sugar becomes converted into it before 
fermentation takes place. The substances which ex- 
cite the vinous fermentation all agree in containing 
a large portion of nitrogen, and in entering readily 
into that state of decomposition, which they commu- 
nicate to sugar. Ripe saccharine fruits contain this 
principle, and their juices, therefore, spontaneously 
enter into the vinous fermentation whenever the 
temperature is favourable. 

503. Alcohol.— C 4 H 6 ? =46.48. The alcohol 
which is the product of this fermentation, may be 
separated from the water, gum, sugar, and other 
principles, with which it is usually associated, by re- 
peated distillations; the last of which must be from 
dry carbonate of potassa, or chloride of calcium. 

20* 



234 PRINCILPES CHEMISTRY. 

Pure or absolute alcohol is a colourless, limpid 
fluid of a penetrating odour, and hot, burning taste. 
It is highly volatile, of the sp. gr. of .795, boils at 
168°, and has never been congealed. It is very in- 
flammable, and burns with a lambent, yellowish- 
blue flame, without smoke. It unites with water 
in every proportion, heat is evolved, and the mixture 
occupies less space than did the alcohol and water 
it contains. Alcohol dissolves the resins, the essen- 
tial oils, the alkalies, and the deliquescent salts. The 
latter crystallize from their alcoholic, in the same 
manner as from their aqueous solution, in combina- 
tion with alcohol of crystallization. The term al- 
coate, is applied to these definite crystalline com- 
pounds. 

From its greater affinity for water, alcohol precip- 
itates gum, and the efflorescent salts, from their 
aqueous solution. 

504. Ether. — C 4 H 5 0. This substance differs 
from alcohol by containing one atom less of water, 
and may be prepared from it by any process which 
will deprive it of that atom. It is usually obtained 
by the action of oil of vitriol on its own weight of 
alcohol. The mixture is quickly raised to the tem- 
perature of 260°, when it boils, and the ether distils 
over, mingled with water and alcohol, from which it 
is freed by a second distillation. In this process the 
oil of vitriol, and alcohol, both part with their water, 
and anhydrous sulphuric acid combines with ether 
to form sulphate of ether. This sulphate combines 
with another atom of oil of vitriol, and forms the 

bisulphateofether,or sulphovinicacid, C 4 H 5 0+S0 3 
+S0 3 +Aq. When this product is heated to 260° it 
is decomposed; the ether escapes in the form of va- 
pour, and the sulphuric acid re-combines with water. 

505. Pure ether is a colourless, limpid fluid, of a 
a hot, pungent taste, and fragrant odour. Its spe- 



ETHER. 



235 



cific gravity is .7; it is very volatile, boiling at 96°, 
and at — 40° in a vacuum. At — 46° it congeals, 
and its evaporation in a cool atmosphere is sufficient 
to freeze mercury. It combines with alcohol in ail 
proportions, but is sparingly soluble in water. It is 
highly inflammable, and burns with a bright white 
flame. It dissolves the essential oils, resins, and fat- 
ty matters, but the fixed alkalies are insoluble in it. 
When a coil of platinum wire is heated to redness, 
and suspended over the surface of ether in an open 
vessel, it sets fire to the stratum of vapour imme- 
diately around it, and is kept at a red heat by the 
combustion until the ether is consumed. 

Phosphoric acid acts on alcohol in the same man- 
ner as sulphuric, forming a phosphovinic acid, which 
is subsequently decomposed; and the ethers which 
the two acids form, are identical in composition and 
properties. 

506. Ether combines with almost all the acids, 
forming compounds which constitute a very natu- 
ral and distinct group of the family of salts. These 
ethereal salts are generally volatile, aromatic fluids, 
freely soluble in oil and alcohol, and more or less 
in water, although some of them are crystalline so- 
lids. The hyponitrite of ethule is the nitrous ether, 
and its alcoholic solution, the sweet spirits of nitre of 
the shops, a highly fragrant, sweet, volatile fluid, 
much used in medicine. 

507. The salt radicals displace the oxygen of the 
protoxide of ethule, and form compounds possessing 
all the generic properties of the ethers. These phe- 
nomena are to be explained by regarding ether as 
the protoxide of an organic radical, C 4 H 5 , which 
has received the name of ethule, and which acts the 
part in composition of an electro-positive element. 
According to this view, the composition of ether is 
C 4 H 5 , 0, and of alcohol C 4 H 5 , O+HO. 

Ethule, ether, and alcohol, are the types of seve- 



236 PRINCIPLES OF CHEMISTRY. 

ral series of organic compounds in which the oxides, 
and the hydrated oxides of compound radicals, pos- 
sess properties closely allied to those of ether and 
alcohol. 

50S. Other products of the decomposition of Al- 
cohol. — When six measures of oil of vitriol are 
strongly heated with two of alcohol, the mass be- 
comes dark, boils rapidly, and finally swells and 
blackens, and a mixture of various vapours and 
gases is copiously evolved. By agitation with 
water, the condensible products, which are sulphu- 
rous acid, ether, and vapour, are removed, and a gas 
remains which is colourless, of an ethereal odour, 
highly inflammable, and burning with a brilliant 
white flame and with much smoke. This gas is the 
olefiant gas, or heavy carbureted hydrogen gas 
of chemists. It detonates violently by means of 
the electric spark, when mixed with three or four 
times its volume of oxygen gas. For each measure 
of olefiant gas, three measures of oxygen disappear, 
water is deposited and two measures of carbonic 
acid gas are formed. These two measures of car- 
bonic acid consist of two of oxygen and two of 
vapour of carbon. The remaining volume of ox- 
ygen combines with two volumes of hydrogen to 
form water; so that olefiant gas contains two vo- 
lumes of vapour of carbon and two of hydrogen 
condensed into one, and its sp. gr. is therefore 
.9868. Its atomic constitution is C 2 H 2 =14.24, or 
according to others, C 4 H 4 =2S.48. 

509. If a jar of olefiant gas be inverted in a pneu- 
matic trough, and bubbles of chlorine be passed up 
into it, both gases disappear, and a heavy oily 
liquid is formed, which may be collected in a cup 
beneath the mouth of the jar. When pure, this 
liquid is colourless, of a sweet ethereal odour, and 
inflammable. It consists of C 4 H 4 C1 2 , and is de- 
composed by an alcoholic solution of potassa, which 



ACETIC ACID. 237 

abstracts an atom of chlorohydric acid, forming 
chloride of potassium, and a gas having a garlic 
odour, and burning with a smoky red flame. The 
composition of this gas is C 4 H 3 C1; so that the oily 
liquid is the chlorohydrate of this substance, and 
must be represented by C 4 H 3 C1+HC1. 

510. Jlcetule. — The chlorine has therefore in de- 
composing the olefiant gas, formed a new radical, 
C 4 H 3 , with which it has combined, forming the chlo- 
ride, C 4 H 3 +C1. This radical has received the name of 
acetule, and is formed from alcohol by other processes. 

511. Jlldehyde. — When alcohol is exposed to the 
action of substances which enable it to combine with 
oxygen, it parts with two atoms of its hydrogen, and 
is converted into a liquid called aldehyde, a neutral, 
inflammable, aromatic fluid, which mixes with water, 
alcohol, and ether. The composition of aldehyde is 
C 4 H 4 +0 2 , and it bears the same relation to acetule 
that alcohol does to ethule; that is to say, it is its 
hydrated oxide, and its composition is represented 
by the formula C 4 H 3 , O+Aq. 

512. Acetic acid. — If the oxidizing process be 
continued, aldehyde combines with two additional 
atoms of oxygen, and is converted into acetic acid, of 
which the formula is C 4 H 3 3 +HO. 

When any fermented liquor is exposed to the free 
access of air at the temperature of 60° or 80°, an 
intestine motion of the particles takes place, the 
liquid becomes turbid, absorbs oxygen, and in the 
end, all the alcohol is found to be converted into 
acetic acid. This acetous fermentation takes place 
with a rapidity proportioned to the free access of 
air; and the changes through which the alcohol 
passes are those which have been recited above; 
aldehyde being always a product intermediate be- 
tween the alcohol and the acetic acid. The change 
is due, in all cases, to the presence of a decomposing 
ferment, which disturbs the equilibrium of the par- 



238 PRINCIPLES OF CHEMISTRY. 

tides of the alcohol so as to bring new affinities into 
play. 

The most concentrated acetic acid which can be 
prepared is the hydrated acid, C 4 H 3 3 +HO. It 
crystallizes at 50° and boils at 240° ; it has a peculiar 
aromatic pungent odour, and a caustic taste; it blis- 
ters the skin, mixes with water, alcohol, and ether, 
and dissolves camphor and the essential oils. Its 
specific gravity is 1.063; by diluting with water it 
acquires the sp. gr. of 1.078, and is then a defi- 
nite compound of the acid, with two additional 
atoms of water. Further dilution reduces its spe- 
cific gravity so that an acid containing 64 per cent, 
of water has the same specific gravity as the most 
concentrated. 

513. The Acetates. — Acetic acid forms salts which 
are all soluble in hot, and most of them in cold water, 
and which are decomposed by sulphuric acid with 
the evolution of acetic acid. The acetate of copper 
is the pigment called verdigris; the acetate of lead, 
the well known salt, sugar of lead. 

514. Pyroligneous Acid. — A pure acetic acid 
known by this name is prepared in considerable 
quantities by the destructive distillation of wood in 
close vessels. It is obtained mingled with tar, em- 
pyreumatic oils, water, pyroxylic spirit, &c, from 
which it is freed by being neutralized by carbonate 
of lime; the acetate of lime precipitates and is de- 
composed by sulphate of soda; the acetate of soda 
which is thus formed, is fused to free it from empyr- 
eumatic oils, and is then redissolved and crystallized, 
and decomposed by oil of vitriol. 

515. Pyroxylic Spirit. — If the liquid from which 
the acetic acid in the above process, has been sepa- 
rated by carbonate of lime, be distilled, a spirituous 
liquid, termed pyroxylic spirit, is obtained, which 
closely resembles alcohol. Pure pyroxylic spirit is 
a colourless aromatic liquid, resembling in smell 



FORMIC ACID. 239 

and taste both alcohol and acetic ether. It burns 
with a paler flame than alcohol, its sp. gr. is 
.798; it boils at 140°, mixes perfectly with wa- 
ter, alcohol, and ether, dissolves the resins and 
essential oils, and is a true alcohol. When treated 
with sulphuric acid it produces an ether, an acid, 
and a heavy ethereal oil, in the same manner as 
alcohol. 

516. Met huh. — These phenomena are explained 
by the supposition of an organic radical called me- 
thule, the formula of which is C 2 H 3 . 

Methylic ether will be represented by C 2 H 3 +0. 
It is a colourless gas of an ethereal odour, highly in- 
flammable, and burning with a blue flame. It is 
eagerly absorbed by water, and is isomeric with 
alcohol, but having half its atomic weight. 

Pyroxylic spirit is the hydrated oxide of methule, 
and is represented by C 2 H 3 0+HO. Methule com- 
bines with the electro-negative elements, and its 
oxide, with the acids, forming a series of compounds 
perfectly analogous to those of ethule. 

517. Formic Acid. — If the vapour of pyroxylic 
spirit be brought into contact with oxygen gas by 
means of spongy platinum, four atoms of oxygen 
are absorbed; two of them enter into combination 
with two of hydrogen, which the other two atoms of 
oxygen replace, and the pyroxylic spirit, C 2 H 4 2 , is 
thus converted into two atoms of water and an atom 
of formic acid, C 2 H 2 4 . This acid derives its name 
from existing in a very concentrated state in the 
common ant. It may be obtained by distilling a 
mixture of one part of starch, sugar, or tartaric acid, 
with four of black oxide of manganese, four of 
water, and four of oil of vitriol. Pure hydrated 
formic acid is a limpid colourless slightly fuming 
liquid, of the sp. gr. of 1.235. It boils at 212°, 
and congeals below 32°. In its most concentra- 
ted state it is exceedingly caustic. It forms crys- 



240 



PRINCIPLES OF CHEMISTRY. 



talline salts, and when the formiates of many of the 
metals are heated, they are decomposed and the metal 
is revived. 

518. Formule. — Formic acid is the oxide of a 
radical called formule, C 2 H; and its composition is 
C 2 H, O+HO. This radical bears the same rela- 
tion to methule which acetule does to ethule. 

519. Oil of Potato Spirit, — There are many sec- 
ondary products of the vinous fermentation of great 
interest to the chemist. Thus the peculiar flavour 
of wine is due to a species of ether, which is the 
only one that is a natural product. The flavour of 
spirit from grain is owing to a peculiar essential oil. 
From the spirit distilled from potatoes, an oil, which 
bears the name of oil of potato spirit, has been sepa- 
rated. This oil, like the pyroxylic spirit, is a genuine 
alcohol. 

It is a colourless oily liquid, with an acrid taste, 
and an aromatic yet nauseous odour, soluble in ether 
and alcohol, and sparingly so in water, burning with 
a blue flame, having a specific gravity of .812, con- 
gealing at 4°, and boiling at 294°. 

520. Jlmule. — The composition of this oil is C 10 
H 12 2 . Sulphuric acid forms with it an ethereal 
oil, and it is evidently the alcohol of a radical of 
which the formula is C 10 H 11 , and to which the 
name of amyle, or amule, has been given. This 
radical combines with chlorine, and its oxide with 
salts, to form true ethers. Its hydrated oxide is the oil 
above described, the proper name of which is amylic 
alcohol By exposure to air this alcohol absorbs 
four atoms of oxygen, and loses two of hydrogen, 
being converted into an acid, C 12 H 10 4 , identical 
with the valerianic acid, which exists naturally in the 
Valeriana officinalis. This is an oily volatile acid, 
lighter than water, and forms soluble sweet-tasted 
salts. 

521. Cetale. — There is a fourth radical of the 



LACTIC ACID. 241 

same family which forms an ether, an alcohol, a 
compound isomeric with olefiant gas, and an acid, 
precisely as in the above cases. This radical is called 
cetule; its constitution is C 32 H 33 ; that of its ether 
C 3 2 H 33 , 0, of its alcohol C 32 H 33 ,0+HO, of its 
olefiant gas C 32 H 32 ,and of its acid C 32 H 31 3 +HO. 
This cetylic alcohol is obtained by the action of al- 
kalies on spermaceti, and is known by the name of 
EthaL It is a tasteless, inodorous, white crystalline 
solid, which melts at 119°, and volatilizes at 250°, is 
insoluble in water, burns like wax, and forms with 
sulphuric acid a compound analogous to sulphovi- 
nic acid. 

The perfect parallelism of the compounds of these 
radicals, methule, ethule, acetule, and cetule, is one 
of the most remarkable and instructive facts, which 
the recent researches into organic chemistry have 
brought to light. 

522. Lactine — Sugar of Milk. — There are other 
species of sugar which naturally belong under this 
head of the alcoholic series. Of these, lactine and 
mannite are the only ones necessary to be noticed. 

Lactine, or sugar of milk, is a secretion found 
only in the milk of animals. It crystallizes in white 
semi-transparent square prisms — of a highly sweet 
taste, slowly soluble in water, and forming a very 
sweet syrup. These crystals contain C 24 H 19 19 -f 
5Aq, and are therefore isomeric with grape sugar, 
having double its atomic number. When heated to 
300°, the sugar of milk fuses, and the 5 atoms of 
water are driven off. Dilute sulphuric acid converts 
it into grape sugar. 

523. Mannite. — Mannite is a secretion from the 
inner bark of many trees. It is obtained from manna 
by the action of boiling alcohol, and crystallizes in 
shining acicular crystals. Its taste is sweet, it does 
not combine with bases, and its formula is C 6 H 7 6 . 

524. Lactic Acid* — When the juice of the beet, 

21 



242 PRINCIPLES OF CHEMISTRY. 

or of the carrot root, which contains much sugar, is 
kept for some time at 100°, a genuine fermentation 
takes place, which is termed the viscous or mucous 
fermentation. Alcohol is not formed in this process, 
but all the sugar disappears, and gum, mannite, and 
lactic acid, are found in its place. The lactic acid 
which is thus formed, is copiously secreted in the 
living animal, and plays an important part in the 
changes which take place in the vital fluids. Pure 
concentrated lactic acid is a syrupy liquid of a strong- 
ly acid taste, the formula of which is C 6 H 5 5 +HO, 
and which is therefore isomeric with sugar of grapes, 
having half its atomic number. When heated to 
4S0°, it parts with the elements of two atoms of 
water, and crystallizes in brilliant white plates, which 
may be purified by solution and crystallization from 
alcohol. Their constitution is C 6 H 4 Q 4 . Lactic acid 
is monobasic, and forms crystalline and soluble salts. 
525. Products of the decay of Lignine. — When 
lignine is exposed to the action of air and moisture, 
its hydrogen slowly consumes, the vegetable struc- 
ture becomes disintegrated, the proportion of carbon 
continually increases, and it is at last converted into 
vegetable mould, or into turf. The principal element 
of mould was originally obtained from the decompo- 
sition of the elm, and received the name of ulmine. 
It is also called humus, and geine, and the acid into 
which it passes by the action of alkalies, the ulmic, 
humic, and geic acid. These products are the ele- 
ments which impart to vegetable mould its fertilizing 
qualities. Products closely allied to them are evolved 
by the action of cold dilute sulphuric acid upon 
starch, sugar, and lignine, and have received the 
names of sacchulmine, and sacchulmic acid. The 
formula of the former is C 40 H 16 14 , and of the lat- 
ter, C 40 H 14 12 . A still longer action of a stronger 
acid converts these products into saccharohumine, 
C 40 H 15 15 , and saccharohumic acid, C 40 H 12 12 . 



LIGHT CARBURETTED HYDROGEN GAS. 243 

These are dark brown, or black substances, resem- 
bling ulmine and ulmic acid. If four atoms of lig- 
nine, C 48 H 32 32 , combine with fourteen of oxygen, 
there will be given out 8C0 2 , and 18HO; and an 
atom of ulmine or geine, C 40 H 14 12 , will remain. 
The formula of the ulmic or humic or geic acid is 
C 40 H 12 12 , being isomeric with the saccharohumic 
acid. This acid is insoluble in water, has a strong 
affinity for ammonia, and other alkaline and earthy 
bases with which it is combined in the soil. It is the 
opinion of Liebig, that it does not enter into the cir- 
culation of plants, but that its fertilizing properties 
are due to the ease with which it is decomposed, and 
the copious supply of carbonic acid it thereby fur- 
nishes. 

526. Light Carburetted Hydrogen Gas. — When 
this decay of woody fibre takes place in shallow 
waters, a peculiar inflammable gas is disengaged, 
which consists of CH 2 ,and is called light carburetted 
hydrogen, or marsh gas. It results from the decom- 
position of lignine by water, one atom of the former, 
C 1 2 H 8 8 , combines with four of the latter, and yields 
6C0 2 , and 6CH 2 . This gas may also be formed by 
heating to redness in a glass retort equal parts of 
acetate of potassa and caustic potassa. The acid 
and water are simultaneously decomposed, C 4 H 3 3 , 
and HO, producing 2C0 2 , and 2CH 2 ; the carbonic 
acid is absorbed by the potassa, and pure light car- 
buretted hydrogen is evolved. It is a colourless, 
transparent, inflammable gas, burning with a yellow 
flame, and forming, with oxygen, a highly explosive 
mixture. It consists of 100 measures of vapour of 
carbon, and 200 of hydrogen, condensed into 100, 
and its sp. gr. is .5593. 

527. This gas is occasionally disengaged in vast 
quantities in coal mines, and forms a highly explo- 
sive mixture by mingling with the atmospheric air. 
It constitutes the fire-damp of the miners, and has 



244 PRINCIPLES OP CHEMISTRY. 

occasioned the most disastrous accidents to those 
engaged in mining for coal. The frequent occur- 
rence of the most melancholy disasters, drew the 
attention of Sir Humphrey Davy to the investigation 
of their cause, and the result of his experiments 
forms one of the proudest triumphs in the annals of 
science. 

Sir Humphrey commenced his inquiries by deter- 
mining the best proportions of air and of light carbu- 
retted hydrogen for forming an explosive mixture. 
This he found to be one of the latter to seven or 
eight of the former. In proportion as the relative 
quantity of either is increased, the mixture detonates 
more feebly, and ceases to explode when the air 
does not form more than three or four times the vol- 
ume of the inflammable gas. On the other hand, 
the mixture continues to be feebly explosive when 
the volume of the air is increased to fourteen times 
that of the gas; while, if the proportion be still fur- 
ther increased, a taper burns in it with only an en- 
larged flame. 

528. Davy next ascertained the temperature re- 
quired for causing an explosion. He found that the 
strongest explosive mixture may be brought into 
contact with iron, and other solid bodies, heated to 
a red and even to a white heat, without detonating, 
provided the solid body is not in a state of combus- 
tion, whereas the smallest point of flame instantly 
causes an explosion. The cause of this difference is, 
that the temperature necessary to produce flame is 
far higher than the white heat of solid bodies; for 
flame is gaseous matter, heated so intensely as to be 
luminous. 

Such being the nature of flame, it follows that 
rapid cooling will immediately extinguish it. Davy 
observed that flame is always extinguished in the 
passage through a narrow tube. He found that the 
narrower the tube, the shorter it may be to produce 



MINERAL COAL. 245 

this effect; and that a plate of brass, pierced with a 
great number of small holes, so as to present in fact 
an assemblage of fine tubes, effectually prevented 
the passage of flame. The gas itself passed, but was 
so much cooled by its contact with the metallic sur- 
face, as to be no longer luminous. 

529. The Safety Lamp. — A piece of fine wire 
gauze was substituted for the plate, and was found 
to be equally impermeable to flame, and this led to 
the construction of the safety lamp. This simple 
contrivance is a common oil lamp, completely sur- 
rounded by a cage of wire gauze. It not merely 
prevents explosion, but indicates the precise moment 
of danger; for when it is carried into an atmosphere 
charged with the fire-damp, the flame begins to en- 
large, and when the mixture becomes highly explo- 
sive, it takes fire as soon as it has passed the gauze, 
and burns on its inner surface, while the light in the 
centre of the lamp is extinguished. The wire gauze 
becomes heated to a red and even to a white heat, 
but does not allow the flame to pass. As soon as 
this appearance is observed, the miner must with- 
draw; for the gauze, which is generally made of 
iron or brass wire, would become oxidated in a few 
minutes, and fall to pieces. 

This beautifully simple and effectual contrivance 
has been the means of preserving the lives of thou- 
sands. The only case in which it has been found to 
fail has been that of a rapid current of air carrying 
the flame through the gauze before it was cooled 
below the luminous point. This is effectually pre- 
vented by surrounding the common safety lamp with 
a glass cylinder, and allowing the air to enter through 
a fine wire gauze at the bottom of the cylinder, and 
to escape through another at the top. 

530. Mineral Coal. — Bituminous coal is the result 
of the decomposition of wood under circumstances 
which do not allow of the escape of the carburetted 

£1* 



246 PRINCIPLES OF CHEMISTRY. 

hydrogens which are formed, and which are therefore 
retained by, or compressed among, the particles of 
the carbon. When bituminous coal is exposed to the 
destructive distillation, these are evolved in the shape 
of tar and bitumen, and, when the heat is sufficiently 
great, of gaseous products consisting of various pro- 
portions of olefiant gas, light carburetted hydrogen, 
and carbonic oxide gases. The gas which is prepared 
by the decomposition of coal in close vessels, for 
the purpose of illumination, is a varying mixture of 
these gases. The composition of bituminous coal is 
C 32 H 12 . When the heat to which the coal has 
been exposed in the interior of the earth has been 
sufficiently great, all the hydrogen is expelled, and 
it is converted into anthracite, which is a nearly 
pure carbon. 

531. Creasote. — The destructive distillation of 
wood tar, gives rise to a great variety of products, 
the only one of which it seems necessary to notice, 
is an oily, colourless, inflammable liquid called crea- 
sote. It has a penetrating odour of smoke, a sharp 
burning taste, and is chiefly remarkable for its power 
of depriving animal substances of their tendency to 
putrefaction. 



Section II. 

THE CAMPHENE SERIES. 

532. The Essential Oils.- — The essential oils which 
are secreted in the living plant, form, together with 
camphor and the resins, a very natural and closely 
allied group of organic products. They agree in 
being highly aromatic, soluble in alcohol and ether, 
and very sparingly, or not at all soluble in water, to 
which they communicate their taste and odour. 
They are highly inflammable, and burn with much 



CAMPHOR. 247 

smoke. They do not form soaps with alkalies, and 
are converted into resins by the absorption of oxygen. 
The essential oils may be divided into three classes; 
those which contain only carbon and hydrogen; those 
containing oxygen and destitute of acid properties; 
and those forming acids. 

533. The oils of the first class form a very re- 
markable group, most of them being isomeric, and 
represented by the formula C 10 H 8 ,or its multiple. 
These isomeric oils yield vapours having the same spe- 
cific gravity 4.766. Oil of turpentine, lemon, copaiva, 
juniper, cubebs, pepper, and bergamotte, are the 
most important of this class. The constitution of 
oil of turpentine is C 20 H 16 ; being identical with 
camphene; that of oiUof cubebs C 15 H 12 ; and that 
of the remainder C 8 H 4 . 

534. The second class contains the oils of cajeput, 
lavender, pennyroyal, the mints, anise, asarum, the 
camphor tree, &c, They consist of, or are resolved 
into, a solid oil called stereoptene, analogous to cam- 
phor, and a liquid oil; the former of which separates 
by long standing. 

535. Camphor — Common camphor is a white, 
semi-transparent, tough, crystalline, volatile solid, of 
a bitter taste and peculiar odour, highly inflamma- 
ble, soluble in ether and alcohol, and sparingly so in 
water. 

Its formula is C 20 H 16 , 2 , being the deutoxide 
of camphene. By boiling with strong nitric acid, it 
is converted into camphoric acid, which crystallizes 
io small rhomboidal tables, has a sour and bitter 
taste, and forms soluble salts. 

536. Camphor is the stereoptene of the oil of the 
camphor tree. Various other oils yield camphor, 
the composition of which varies with its origin. 
Those of peppermint, anise, and fennel, are isomeric 
with their oils, those of turpentine, and asarum, are 
their hydrates,and those of camphor, and most others, 
their oxides. 



248 PRINCIPLES OF CHEMISTRY. 

When chlorohydric acid gas is passed into oil of 
turpentine, they combine and form a white crystal- 
line solid, smelling strongly of camphor, which is 
called artificial camphor, from its resemblance to that 
body. 

537. The Resins. — The resins appoach closely to 
the camphors in constitution and properties, but dif- 
fer in being decomposed before they are volatilized, 
and in possessing acid properties w r hich enable them 
to combine with alkalies and form a species of soap. 
They are produced by the oxidation in the living 
plant itself, of essential oils isomeric with oil of tur- 
pentine. They mostly exude naturally from the 
living plant, in which case several distinct products 
are usually blended together.* 

538. The most important are common rosin, co- 
pal, mastich, sandarac, guaiacum, copaiva, amber, 
olibanum, caoutchouc, and dragon's blood. The 
principal use of the resins is in the preparation of 
varnishes. 

539. Caoutchouc. — This is the most singular, and 
promises to be the most useful, of all these resins. 
It is a soft, tenacious, inflammable solid, remarkable 
for its great elasticity. It is insoluble in alcohol and 
water, but soluble in essential oils and in the volatile 
liquid obtained from its decomposition by heat in 
close vessels. It thus yields a varnish capable of 
being applied to the softest fabrics, and surpassing 
all other known bodies in the degree in which it 
combines insolubility, flexibility, elasticity, and re- 
sistance to the ordinary causes of change and decay. 

540. Benzule. — The third class of essential oils 
contains the oils of bitter almonds, of cloves, of cin- 
namon, and of the spiraea ulmaria. The careful 
examination to which these oils have been subjected, 
has thrown much light on the laws of organic com- 
bination. The oil of bitter almonds is a feeble acid, 
the base of which is hydrogen, and the electro-nega- 



OIL OF BITTER ALMONDS. 249 

tive element is a complex radical called benzule, of 
which the formula is C 14 H 5 2 ,and the symbol, Bz. 
This radical combines with the simple elements 
chlorine, iodine, bromine, and sulphur, forming com- 
pounds which are neither acid nor basic. ■ 

541. Benzoic Acid. — Its protoxide is the benzoic 
acid, BzO, which exists in combination with resin in 
what are called the Balsams, viz. gum benzoin and 
storax, and the balsams of Peru and Tolu. 

Benzoic acid is a volatile, inflammable acid, hav- 
ing a fragrant odour when heated, and a sweet, aro- 
matic taste. It is soluble in alcohol and water, and 
crystallizes in needles of a silky lustre. It is a mono- 
basic acid, from which the atom of base cannot be 
separated, and the formula of its salts is M, Bz0 2 . 

542. Oil of Bitter Almonds. — This oil does not 
exist ready formed in the plant, but is evolved in the 
decomposition of amygdaline, an albuminous solid, 
which forms a principal portion of the kernels of the 
bitter almonds. When these are macerated in water 
and distilled, the amygdaline disappears, and oil of 
bitter almonds, cyanohydric and formic acids, and 
sugar, are formed. The oil of bitter almonds is a 
colourless, transparent, inflammable fluid, of a strong, 
peculiar odour, and burning taste, which absorbs 
oxygen from the air, and is converted into benzoic 
acid. It unites with various bases, and undergoes 
a series of highly interesting changes by the action 
of different reagents. It seems probable that the 
true radical in all these products is C 14 H 5 ; of which 
benzule is itself the deutoxide. 

553. The oil of cinnamon is the compound of a 
peculiar radical, cinnamule, C 1 8 H 7 2 , withhydro- 
gen, and, like the oil of bitter almonds, it may be re- 
garded as a feeble acid. Cinnamule unites with an 
atom of oxygen to form an acid very similar to ben- 
zoic acid, and combines also with chlorine. 

544. The oil of the spiraea ulmaria is similar in 



250 PRINCIPLES OF CHEMISTRY. 

constitution, being the hyduret of saliciile, a com- 
plex radical, represented by C 14 H 5 4 , which may 
be regarded as the deutoxide of benzule. 



Section III. 

THE OILY ACIDS. 

545. The fixed oils, whether of vegetable or ani- 
mal origin, closely resemble each other in composi- 
tion. The animal oils are chiefly deposited in the 
cavities of the cellular tissue, and the vegetable oils 
in and around the seed. They cannot be volatilized 
without decomposition, and they all form soaps with 
the alkalies. By exposure to the air, one class of 
these oils, called the drying oils, absorb oxygen, and 
become converted into an elastic, tough solid, which 
renders them useful in painting. 

The fixed oils are nearly inodorous and tasteless; 
their density varies from .9 to .96. Some of them, 
as the animal fats, palm oil, and cocoa-nut oil, are 
solid at common temperatures, but become fluid at 
a gentle heat. At 600° they begin to boil, suffering 
a partial decomposition, and disengaging an inflam- 
mable vapour at the same time. When heated to a 
red heat, in a close vessel, they are decomposed and 
evolve large quantities of olefiant gas. In the open 
air they burn with a clear and bright flame, and are 
converted into water and carbonic acid. 

The fixed oils are insoluble in water, but may be 
permanently suspended in that liquid by means of 
mucilage or sugar. This mixture is termed an emul- 
sion. They are in general sparingly soluble in alco- 
hol and ether, although castor oil is soluble in all 
proportions in the former. 

546. The fixed oils absorb oxygen gas when ex- 



STEARINE. 251 

posed to the air, and become thick and rancid. The 
oil of flax-seed, hemp-seed, nut oil, and some others 
of the fixed oils, are called drying oils, because they 
are at length converted by this process into an elas- 
tic, gummy mass. It is this property which renders 
these oils valuable in painting, in the preparation of 
varnishes, and the manufacture of printer's ink. 
This absorption of oxygen by the drying oils is 
under some circumstances so abundant and rapid, 
and accompanied by the extrication of so much heat, 
as spontaneously to kindle easily inflammable sub- 
stances, with which they may be mixed. Many 
extensive fires have been caused by carelessly spill- 
ing drying oils on lamp-black, cotton, flax, wool, or 
even shavings of wood. 

The fixed oils combine with the alkalies and me- 
tallic oxides; their combination with the alkalies 
forms soap, and that with the metallic oxides, more 
particularly with the oxide of lead, forms the plas- 
ters of the pharmacopseias. 

547. The experiments of Chevreul have shown 
that fixed oils consist of three proximate elements; 
two of them solid and crystalline, and the other re- 
maining fluid at low temperatures. These principles, 
which closely resemble each other, are named stea- 
rine, margarine, and oleine. They consist of organic 
acids combined with an organic base called glycerine. 

548. Stearine. — Stearine is obtained from mutton 
suet by the crystallization of the hot ethereal solu- 
tion. It is crystalline like spermaceti, not greasy to the 
touch, soluble in ether and alcohol, and fusing at 143°. 
Stearine is found to be a bi-stearate of glycerine, 
and its formula is C 142 H 141 , O i7 , or C 6 H 7 5 + 

2C 6 8 H 66 5 +2Aq. Pure stearic acid is tasteless, 
and inodorous. It is soluble in alcohol but not in 
water, and crystallizes from its alcoholic solution in 
brilliant white plates, of a pearly lustre. Stearic 



252 PRINCIPLES OF CHEMISTRY. 

acid has a feeble reaction, its solution turns vege- 
table blues red, and it decomposes the alkaline car- 
bonates. It melts at 158°, and congeals into a crys- 
talline mass, which burns with a clear white flame, 
and is extensively manufactured as a substitute for 
wax and spermaceti for candles. Stearic acid is a 
bibasic acid, and the formula of its salts is M 2 + 
C 68 H 66 7 . The alkaline stearates are the only 
ones soluble in water. 

549. Margarine. — Margarine is found with stea- 
rine, though in smaller proportions in most animal 
and vegetable oils. It is the principal ingredient of 
human fat. It closely resembles stearine, but fuses 
at 118°, and is more soluble in ether and alcohol. 
Margaric acid crystallizes in white needles, and 
fuses at 140°. It is a monobasic acid, and its for- 
mula is C 34 H 33 ,0 3 +Aq. 

550. Oleine. — Oleine exists in conjunction with 
stearine and margarine in almost all oils and fats. It 
is soluble in cold alcohol, and may thus be obtained 
separately. It remains fluid at 0°, and exists nearly 
pure in almond oil. It is a binoleate of glyce- 
rine, and its formula is C 94 H 37 15 =:C 6 H 7 5 +2 

C 44 H 39 4 +2Aq. The oleic acid is an oily liquid 
having a slight smell and a pungent taste. It is acid 
to test paper, soluble in ether and alcohol, and crys- 
tallizes in needles when cooled below 32°. The for- 
mula of oleic acid is C 44 H 39 4 +HO. 

551. Glycerine. — These acids exist in nature iri 
combination with an oxide of hydrocarbon, which 
has received the name of glycerine. This is sepa- 
rated during the process of saponification, and may 
be obtained in combination with an atom of water. 
The hydrate of glycerine is an inodorous syrupy 
liquid, of the sp. gr. of 1.27, and very sweet to the 
taste. It is insoluble in ether, but miscible in all pro- 
portions with water and alcohol. Its solution is inca- 



NATIVE ORGANIC ACIDS. 



253 



pable of being fermented. Its formula is C 6 H 7 5 + 
Aq. Glycerine, therefore, differs from mannite in 
containing one atom more of oxygen. 

552. The various soaps of commerce are the stear- 
ates, margarates, and oleates of potassa and soda. 

The salts of soda are the hard white soaps, and 
those of potassa are a semi-transparent gelatinous 
mass. Yellow soap contains about one-third of resin 
to two of fat. 

Almost every variety of oil and fat, contains, along 
with stearine, margarine, and oleine, a larger or 
smaller portion of a peculiar acid, which belongs to 
the same group as those above described, has simi- 
lar reactions with the bases, and is combined in a 
state of nature with glycerine. 



Section IV. 

NATIVE ORGANIC ACIDS. 

553. It would swell an elementary treatise be- 
yond its proper size, to attempt to treat of the great 
variety of native acids which have been discovered, 
and their bare enumeration would be useless. All 
that can be done, is to point out the properties of the 
most important. 

554. The views which have been unfolded re- 
specting the nature of active acids, and of salts, are 
placed in still clearer light by the constitution of the 
organic acids. All these acids are what is called 
hydrated, that is, exist in combination with one or 
more atoms of water, which are essential elements 
of their constitution. The number of basic atoms in 
the salts which they form, is always determined by 
the atoms of this basic water, and the hydrated acid 
may be regarded as a salt of hydrogen. These views 

22 



254 PRINCIPLES OF CHEMISTRY. 

are further strengthened by the changes which take 
place in tartaric acid, which is the only organic acid 
from which we are able to expel all the water. la 
its anhydrous state, it is destitute of acid properties, 
and is insoluble in water. 

555. Pyrogenous Acids. — When these acids are 
submitted to the action of strong heat in a close ves- 
sel, they give rise in most cases to new acids, which 
are called, from the circumstances in which they are 
formed, the pyrogenous acids. Thus, citric acid, 
C 12 H 5 11 +3Aq, when heated, is converted into 
pyrocitric acid, C 4 H0 3 +H0, which is identical with 
the aconitic acid, that exists in the aconitum napel- 
lus, or wolfs bane. 

556. Tartaric Acid. T. — This acid exists natu- 
rally in combination with lime or potassa, in the 
juices of several fruits. It is found in the grape in 
the form of bitartrate of potassa, and as this salt is 
less soluble in alcohol than in water, it is deposited 
during the fermentation of the juice of the grape, 
and has long been known in commerce by the name 
of crude tartar, or when purified and pulverized, by 
the name of cream of tartar. Tartaric acid has 
strong acid properties; it is very soluble in water, 
crystallizes in rhomboidal prisms, which are perma- 
nent in the air, and may be distinguished from all 
other acids by forming white granular crystals, when 
added to a solution of potassa or any of its salts. 
The formula of tartaric acid is C 8 H 4 10 +2HO. It 
is a bibasic acid, and the constitution of its salts is 
C 8 H 4 12 +M, H, or2M. 

The bitartrate of potassa, KO, HO+T, the com- 
mon cream of tartar of the shops, is a natural secre- 
tion of the grape, and being insoluble in alcohol, it 
is precipitated during the fermentation of the juice. 
It is sparingly soluble in water. The basic tartrate, 
2KO+T, is the soluble tartar of the shops. Rochelle 



RACEMIC ACID. 255 

salt is the double tartrate of potassa and soda, KO, 
NaO+T. 

557. Tartar emetic is the tartrate of potassa and 
antimony, KO, St 2 3 +T+2Aq; this water is driven 
off at 212°, and when the salt is heated to 480°, two 
additional atoms of water are formed, which must 
arise from the disintegration of the salt, as they are 
restored when it is again dissolved. The real con- 
stitution of tartar emetic is not understood; and is 
difficult to reconcile with the binary theory of salts, 
which supposes the active acid to be a salt of hydro- 
gen, and that the ordinary salts are formed by the 
union of the oxygen of the base with this hydrogen. 
To explain the constitution of tartar emetic on this 
theory we must suppose tartaric acid to be quadri- 
basie and not bibasic, as is the fact. The boracic 
acid unites as a base with the bitartrate of potassa 
to form a double salt, which presents the same theo- 
retical difficulties as tartar emetic. 

558. Tartaric acid is changed by fusion into an 
isomeric acid called the tartralic, of which the 
atomic number is one and a half times that of tar- 
taric acid. By longer fusion it loses all its water 
and is converted into a porous white mass, insoluble 
in water and alcohol, and destitute of acid proper- 
ties. When distilled at still higher temperatures, it 
is converted into a monobasic acid — the pyrotar- 
taric, of which the constitution is C 5 H 3 3 . 

559. Eacemic Acid. — The wines of the Vosges 
mountains in France, deposit during certain seasons, 
a peculiar salt of potassa, the acid of which is not 
the tartaric, but an isomeric acid, the racemic. It 
is less soluble than the tartaric acid, and its salts differ 
in crystalline form from the tartrates. It forms a 
parallel series of salts with the tartaric acid, and has 
the same combining number, although it is said by 
Fresenius to be a monobasic, and not a bibasic 
acid. 



256 PRINCIPLES OF CHEMISTRY. 

560. Citric Jicid. Ci. This acid exists in the 
juices of the lemon, the gooseberry, and other fruits. 
It has an agreeable sour taste, is soluble in less than 
its weight of cold water, and usually crystallizes in 
large rhombic prisms, containing two atoms of water 
of crystallization. It is a tribasic acid; its formula 
being C^K^O^+SHO; and that of its salts, C 12 H 5 
14 +M 3 , M 2 H, or MH 2 . Citrate of soda consists 
of C 12 H 5 14 , Na 3 +4Aq+7Aq. At 212° the seven 
atoms of water are driven off, and the remaining four 
are not parted with, till the heat is raised to 400°. 

The pyrocitric acid has already been noticed. 

561. Malic Acid. — This acid exists along with 
citric acid, in the berries of the mountain ash and 
other fruits. It is strongly acid and deliquescent. 
It is a bibasic acid, its constitution being C 8 H 4 8 + 
2HO, and that of its salts, CgH^ +M 2 , or MH. 
When heated it gives out two atoms of water, and 
is converted into two acids, one of which, the MaZeic, 
is a bibasic acid, isomeric with the aconitic, and hav- 
ing double its atomic number, viz. C 8 H 2 6 +2HO. 
The other is a monobasic acid, of which the formula 
is C 4 H0 3 +H0. It is identical with the fumaric 
acid which exists naturally in the fumitory, and in 
Iceland moss. 

562. Tannic Acid — This acid principle is the 
chief cause of the astringency of vegetable sub- 
stances. It exists abundantly in the inner bark of 
the oak, in gall nuts, in the inspissated juices, kino 
and catechu, and in the seeds of the grape. Pure 
tannic acid is prepared by submitting finely pow- 
dered gall nuts to the action of cold ether. The 
water contained in ether combines with the tannic 
acid, while the remaining proximate principles of 
the gall nuts are dissolved by the ether. The aque- 
ous solution, which forms a dense stratum at the 
bottom of the vessel, is separated and carefully evapo- 
rated to dryness. Pure tannic acid is colourless and 



GALLIC ACID. 257 

inodorous, has a purely astringent taste without bit- 
terness, and may be preserved dry without change. 
It is very soluble in water, and the solution reddens 
litmus paper, and decomposes the alkaline carbo- 
nates. Tannic acid forms a salt of a deep blue 
colour with the peroxide of iron, and combines with 
many other of the metallic oxides. 

Tannic acid is distinguished from all other sub- 
stances by forming with gelatine a compound which 
is insoluble in water. This compound, which is 
called leather, is formed whenever the skins of ani- 
mals, which consist chiefly of gelatine, are exposed 
to the continued action of a solution of tannic acid. 
Leather, when dried, becomes tough and hard, and 
resists putrefaction. 

The salts of tannic acid are remarkable for their 
peculiarities of colour; and it is on this account 
highly useful as a test. It is a tribasic acid, its 
formula being C 18 H 5 9 +3HO. 

563. Gallic Acid. — This acid is obtained by boil- 
ing for a few minutes an infusion of gall nuts with 
a strong solution of potassa, and adding an excess of 
sulphuric acid, which causes a copious precipitate 
of gallic acid. This acid is bibasic, and its formula 
is C7HO3+2HO. It is also formed by the decom- 
position of a solution of tannic acid, which absorbs 
from the air 8 atoms of oxygen, and forms 4 C0 2 , 
2C 7 H0 3 , 2HO, and HO. Three atoms of tannic 
acid contain the elements of six atoms of gallic acid, 
and one atom of grape sugar. 

564. Pure gallic acid has a weak acid and astrin- 
gent taste, and reddens litmus paper. It is freely 
soluble in boiling water, but requires 100 parts of 
cold water to dissolve it. The pergallate of iron is 
a salt of a deep blue colour; common writing ink is 
a mixed solution of the pertannate and pergallate of 
iron. Gallic acid does not precipitate solutions of 

22* 



258 PRINCIPLES OF CHEMISTRY. 

gelatine, as does the tannic acid. When anhydrous 
gallic acid is exposed to a heat of 419°, it is decom- 
posed into one atom of carbonic acid, and one of 
pyrogallic acid, consisting of C 6 H 3 3 . This acid 
sublimes and condenses into brilliant, white, scaly- 
crystals. It is more soluble than gallic acid, and 
strikes a blackish blue colour with the persalts of 
iron. When pyrogallic acid is heated to 480°, it is 
decomposed; two atoms yielding three atoms of 
water, and one atom of metagallic acid, C 12 H 3 3 . 
Metagallic acid is a black, shining, insoluble mass, 
that is dissolved by the alkalies, and forms neutral 
salts, most of which are black and insoluble. During 
the process for the preparation of gallic acid, another 
modification of that acid subsides in the form of an 
insoluble gray powder. It has been called ellagic 
acid, and consists of C T H0 3 +HO, containing one 
atom less of water than the gallic acid. 

565. Pectic Jicid. — When the filtered juice of cer- 
tain plants, such as the carrot or the beet, is mixed 
with alcohol, a gelatinous mass subsides, which may 
be collected on a filter, washed, and dried. It then 
forms a transparent, insipid mass, one part of which 
forms a firm jelly with one hundred parts of water. 
This vegetable jelly is called pectine. By long boil- 
ing it changes into pectic acid; which exists in plants 
as a pectate of lime, and may be obtained from their 
juice by the action of chlorohydric acid. Pectic 
acid is obtained in white transparent scales, acid to 
the taste, and reddening litmus paper. Its solution 
does not gelatinize, but is converted into a firm jelly 
by acids, lime water, and sugar. It is a bibasic acid, 
isomeric with pectine, and its formula is C 22 H 17 
22 +2HO. 



FIBRINE. 259 

CHAPTER IV. 

NITROGENOUS COMPOUNDS OF CARBON AND HYDROGEN. 

Section I. 

IMMEDIATE ORGANIC PRODUCTS. 

566. The principal distinction between animal and 
vegetable products, is the presence in the one case, 
and the absence in the other, of nitrogen. Many 
animal secretions, however, such as the fatty oils, 
are destitute of nitrogen, and many vegetable pro- 
ducts, such as gluten, and the organic alkalies, con- 
tain it. The presence of nitrogen renders the sub- 
stances more liable to putrefaction, and greatly com- 
plicates the results of decomposition. 

567. Fibrine, albumen and caseine, are to animals, 
what lignine, gum, starch, and sugar, are to vegeta- 
bles; their most copious and important secretions, 
products essential to the life and health of the indi- 
vidual. 

56S. Fibrine. — Fibrine constitutes the basis of the 
flesh of animals, and is deposited in the muscular tissue 
from the blood, of which it forms a principal constitu- 
ent, andin whichit remains during life in a liquid state. 
It may be obtained by stirring freshly drawn blood 
with a bundle of twigs, to which the fibrine adheres 
in soft tenacious masses; and it is purified by wash- 
ing in water, and digesting in alcohol and ether. 
When dried at a gentle heat, it is a yellowish, opaque, 
tasteless, insoluble mass, which undergoes no change 
when kept in dry air. In the damp it absorbs so 
much water as to treble its weight, and become soft, 
elastic, and flexible. When long boiled in water it 
is decomposed and dissolved. 

569. Fibrine absorbs cold oil of vitriol, and forms 



260 PRINCIPLES OP CHEMISTRY. 

with it a neutral compound soluble in water. It is 
dissolved in acetic acid, and by caustic potassa; and 
when exposed to the damp speedily undergoes putre- 
faction. 

570. Gluten. — When the newly expressed juices 
of vegetables are allowed to stand, a green gelatinous 
precipitate is formed, which becomes by the removal 
of the colouring matter, a grayish white substance, 
having all the properties of fibrine. This fibrine is 
contained in large quantities in the juice of grapes, 
and in the seeds of the cerealia. The gray, viscid, 
fibrous, elastic mass, which remains after the starch 
has been separated from wheat flour, is nearly pure 
fibrine, and bears the name of Gluten. Boiling alco- 
hol separates it from the albumen with which it is 
mixed, and the pure gluten may be precipitated 
from the solution by water. Pure gluten is insolu- 
ble in water and ether, but forms a thick syrupy 
solution in alcohol, and dissolves in acetic acid, 
and alkaline solutions. When dry it is a hard, brit- 
tle mass of a yellow colour, which undergoes no 
change in dry air, but absorbs moisture in the damp, 
swells, becomes a soft, adhesive, elastic mass, which 
soon ferments and undergoes putrefaction. 

571. *dlbumen. — This substance is diffused through- 
out the whole animal frame, and exists in two con- 
ditions, a soluble, and an insoluble one. Soluble 
albumen is in its purest form in the white of eggs, in 
which it is united with water, carbonate of soda, and 
saline matter. Liquid albumen is a thick, glairy 
fluid; insipid, inodorous, easily miscible with water, 
and perfectly soluble in a large quantity of that fluid. 
When dried at a low temperature, it becomes a solid, 
transparent mass, which retains its solubility. At 
160°, albumen is coagulated, as it is also by alcohol, 
and the stronger acids. Dr. Turner supposes that 
liquid albumen is a solution of albumen in water, 
formed at the moment of being secreted, but that the 



CASEINE. 26 1 

union is so feeble as to be broken by slight causes, 
which render the albumen quite insoluble, without 
effecting any change in its composition. The solu- 
bility of nascent silica, and its insolubility under all 
other circumstances, furnish an analogous case. 
Water diluted with T ^^ of its weight of albumen, is 
rendered opaque by boiling. Solutions of albumen 
coagulate at 212°, and are much used for clarifying 
turbid solutions; for the coagulated albumen carries 
with it, to the surface, the foreign particles which 
render the liquid turbid. Albumen is precipitated 
by several of the metallic salts, and is a useful test 
of the presence of corrosive sublimate, with which it 
forms an insoluble, inert precipitate. It is, there- 
fore, an effectual antidote to the effects of that poison. 
So delicate a test is this chloride of the presence of 
albumen, that it will occasion a milkiness in water 
containing only 20V0 P art of albumen. The precip- 
itate is said to be a combination of oxide of mercury 
and albumen. Albumen may also be obtained from 
the liquid, which has been used in the separation of 
fecula from wheat flour. If the water, from which 
the starch has been deposited, be heated, it will be- 
come more or less cloudy, and white films separate, 
which have all the properties of coagulated albu- 
men. It exists in plants in only small quantities; 
the seeds of the cerealia contain from T \-th to 31 per 
cent, the leaves of the cabbage, the stalksof asparagus, 
and the roots of turnips, yield it in larger quantities. 
The albumen from vegetables is destitute of elas- 
ticity when softened, and dries into a hard, white 
mass. It is soluble in water; its solution is coagu- 
lated by heat, and it has all the properties of ani- 
mal albumen. 

572. Caseine. — This element is the principal sub- 
stance of the curd of cheese, from which it may be 
obtained by digestion in water, and in alcohol, which 
dissolve out the foreign substances, with which it is 



262 



PRINCIPLES OF CHEMISTRY. 



mixed. Caseine dries into a semi-transparent, yellow- 
mass, and is perfectly insoluble both in cold and 
hot water; although soluble in water to which acetic 
acid, or an alkali, has been added. It is unalterable 
in a dry atmosphere, and the changes which old 
cheese undergoes, are due to the foreign substances 
mixed with the caseine. Caseine also exists in the 
seeds of leguminous plants. 

573. Fibrine, albumen, and caseine, like starch, 
gum, and sugar, closely resemble each other, and 
may be converted one into the other. By digestion 
at 80° in a solution of nitre, fibrine acquires the prop- 
erties of liquid albumen; and caustic potassa throws 
down liquid albumen in the form, and with the pro- 
perties of caseine. In the living organism, these 
principles are all liquid: the fibrine coagulates by 
mere exposure to the air, the albumen by heat, and 
the caseine by the addition of rennet, or an acid. 

When these substances are dissolved in a solution 
of caustic potassa, and then exposed for some time 
to a high temperature, the addition of acetic acid, 
causes all the organic matter to fall in a gelatinous, 
translucent precipitate, of exactly the same charac- 
ter in all cases. 

574. Proteine, — This substance, to which the name 
of proteine (the first element) has been given, is com- 
mon to all these compounds, and the ultimate analysis 
of proteine, albumen, fibrine, and caseine, gives abso- 
lutely the same proportions of carbon, hydrogen, 
nitrogen, and oxygen, with small and varying quan- 
tities of sulphur and phosphorus. The formula, 
which, according to Liebig, best represents the com- 
position of proteine (Pr) is, C 48 N 6 H 36 14 . Caseine 
differs from proteine in containing a minute quantity 
of sulphur; albumen and fibrine differ from it in 
containing sulphur and phosphorus; and their com- 
position will be represented thus ; caseine, Pr+S; albu- 
men, Pr+P+S; and fibrine, Pr+P+2S. The quan- 



BONES. 263 

tities of sulphur, and phosphorus in the above for- 
mulae do not represent equivalents; for were they so 
framed as to do this, the formulae would thus stand; 
caseine, Pr 20 (C 960 N 120 , H 720 O 280 )+S; albu- 
men, Pr 20 +P+S; and fibrine, Pr 20 +P+S 2 . These 
numbers startle us by their magnitude, for they make 
an atom of fibrine to contain 2083 elemental atoms : 
and it is much safer in the present state of our know- 
ledge, to take the simple statement of Liebig, as a 
sufficiently close representation of facts. 

575. Gelatine. — Gelatine exists abundantly in 
many of the solid parts of animals, such as the skin, 
bones, and cartilages. It does not appear to exist in 
any of the animal fluids. It is distinguished from 
all other animal principles by its ready solubility in 
boiling water, and by the bulky, semi-transparent 
jelly, which the solution forms on cooling. One 
part of gelatine, dissolved in 100 parts of water, be- 
comes solid on cooling. Isinglass, which is the dried 
air-bladder of the sturgeon, is the purest form of 
gelatine; common glue is gelatine prepared from the 
skins and hoofs of animals. Gelatine is soluble in 
most of the diluted acids, and in alkaline solutions; 
concentrated sulphuric acid dissolves it without char- 
ring, and converts it into a peculiar saccharine prin- 
ciple, which is soluble in water, and in alcohol, 
and crystallizes in large prisms, which consist of 
C 16 H 15 N 4 11 +3Aq. The composition of gela- 
tine itself is calculated by Liebig, from Mulder's an- 
alysis, to be, C 54 N 9 H 42 20 . 

If a solution of common salt, and one of alum, be 
poured into a solution of gelatine, the latter falls 
down in combination with alumina. On this prin- 
ciple is founded the manufacture of white leather, by 
the process called tawing. 

576. Bones. — Gelatine constitutes about one third 
of the solid material of bone, and may be separated 
from the earthy skeleton which envelopes it, by long 



264 PRINCIPLES OF CHEMISTRY. 

digestion in boiling water. The earthy skeleton 
consists, indifferent animals, of from 80 to 95 per 
cent, of phosphate of lime, from 2 to 20 per cent, of 
carbonate of lime, a small portion of carbonate of 
soda and magnesia, and a trace of fluoride of calcium. 
The phosphate of lime yields by analysis, 8 atoms of 
lime, and 3 of phosphoric acid. The acid is the tri- 
basic acid, and Graham supposes the bone phosphate 
to be a combination of two phosphates; viz: 2 (3Ca 
0, P 2 5 +Aq)+(H0, 2Ca 0, P 2 5 +Aq). 



Section II. 

CYANOGEN. 

577. When any of the foregoing animal matters 
are calcined with potash, there is obtained by lixivia- 
tion and evaporation, a yellow crystalline salt, which 
has long been known as yielding with sulphate of 
iron, the beautiful pigment, prussian blue. When 
this prussian blue is boiled with half its weight of 
red oxide of mercury in four parts of water, the clear 
solution yields by evaporation, colourless, prismatic 
crystals. These crystals are a combination of mer- 
cury, with the substance which was combined with 
potassa and iron, in the prussian blue. 

578. By heating the crystals in a glass flask con- 
taining no lead, the mercury is volatilized, and a 
gas escapes which may be collected over mercury. 
It is colourless, of a peculiar odour, and irritates the 
eyes. Its sp. gr. is 1.816; it extinguishes burning 
bodies, but is itself inflammable, and burns with a 
beautiful purple flame. When 100 measures of this 
gas are mixed with 200 measures of oxygen, and 
exploded, the products are 200 measures of carbonic 
acid, and 100 of nitrogen. The former contains 200 



CYANIC ACID. 265 

measures of vapour of carbon, so that the gas con- 
sists of 200 vapour of carbon, and 100 nitrogen, con- 
densed into 100 measures. It is therefore a bi-car- 
buret of nitrogen, and its formula is N C 2 =26.39. 

579. From its close affinity to the simple elements, 
and the multitude of its combinations, it has received a 
simple elemental name, and is called cyanogen from 
xvavo$, blue, and y$+w*a, I generate, and its symbol 
is Cy. Beneath the pressure of four atmospheres, 
cyanogen becomes a limpid fluid. It supports a 
strong heat without decomposition. At 60°, water 
absorbs 4.5 times, and alcohol 23 times its volume. 

580. Paracyanogen. — When the bicyanide of 
mercury is decomposed by heat, a brown carbona- 
ceous mass is left in the retort, which is found to 
have the same composition as cyanogen, but which 
yields very different products by the action of the 
same reagents. This solid carburet of nitrogen, 
which is isomeric with cyanogen, has received the 
name of paracyanogen, and its formula is N 4 C 8 . 

581. Cyanogen belongs to the class of salt radi- 
cals; it forms true haloid salts with the metals, and 
although it cannot be made to unite directly with 
oxygen, it can be indirectly combined with it, and 
forms a very remarkable group of isomeric acids. 

582. Cyanic Acid. — CyO=34.39. Cyanic acid 
is obtained in combination with an atom of water, 
and is liquid, with a penetrating, pungent odour, 
like that of strong acetic acid; it excoriates and blis- 
ters the skin, is very volatile, and has strong acid 
properties. 

Cyanic acid is remarkable for the facility with 
which its solution is converted into carbonic acid and 
ammonia. One atom of the acid combines with 
three atoms of water, and is resolved into two atoms 
of carbonic acid, and one of ammonia. 

Cyanic acid is a monobasic acid, and forms crys- 
talline salts of considerable permanency.' 

23 



266 



PRINCIPLES OF CHEMISTRY. 



583. Fulminicrfcid.—Cy 2 2 +2E.0=68.78. This 
acid has never been insulated, and is known only in 
combination. It is a bibasic acid, and forms salts 
remarkable for the instability of their constitution. 
The most remarkable of these are the fulminates of 
silver and mercury. The former is prepared by 
dissolving silver in 10 parts of nitric acid, sp. gr. 
1.35, and pouring the cold solution into 20 parts 
of alcohol. The mixture is made to boil gently, 
and is then slowly cooled, when it deposits the 
fulminate of silver in snow white, silky crystals. 
The formula of this salt is Cy 2 2 +2AgO. It deto- 
nates violently by the slightest friction, and by con- 
tact with sulphuric acid. The fulminate of mercury 
is prepared from a solution of mercury in nitric acid, 
in the manner above described. Its formula is 
Cy 2 2 +2HgO. It explodes by a smart blow, and 
is the salt used in the percussion guns. The paste 
with which the percussion caps are filled, is prepared 
by finely triturating 10 parts of the salt, with 30 of 
water, and then thoroughly mixing the soft mass 
with six parts of nitre. 

584. Cyanuric Acid.— Cy 3 O 3 +3HO=103.17. 
This acid is obtained by dissolving the solid chloride 
of cyanogen in water. It is colourless, inodorous, 
and sparingly soluble in water. It feebly reddens 
litmus paper, and crystallizes in rhombic prisms, 
which contain 4 equivalents of water of crystalliza- 
tion permanently. It is a tribasic acid and forms sol- 
uble salts. The cyanurate of silver, 3AgO+Cy 3 3 , 
may be heated to 600° without decomposition. 

585. When dry cyanuric acid is heated to low 
redness in a retort, it is decomposed into hydrated 
cyanic acid, which distils over, and may be collected 
in a receiver surrbunded by a freezing mixture. As 
soon as the vessel has acquired the common temper- 
ature, a violent molecular agitation, accompanied 
with a great rise of temperature, takes place, and the 



METALLIC CYANIDES. 267 

liquid is transformed into a white, porcelanous mass, 
which is insoluble in water, alcohol, and ether, and 
which is reconverted into hydrated cyanic acid by 
again exposing it to great heat. 

586. The apparent isomerism of the oxygen acids 
of cyanogen, is very satisfactorily explained by the 
new views of the constitution of salts and acids. 
According to these views the formula of the cyanates 
is M+Cy0 2 ; that of the fulminates, 2M, or M, H+ 
Cy 2 ; and that of the cyanurates, 3M, M 2 H, or 
MH 2 +Cy 3 6 . 

5S7. Cyanohydric Acid. — Hydrocyanic Acid. — 
Prussic Acid. — Cyanide of Hydrogen. — CyH= 
27.39. This acid may be formed by the direct union 
of its elements; it is found native in combination 
with the oil of bitter almonds, and in the water dis- 
tilled from the leaves of peaches, the wild cherry, 
and the cherry laurel. It is also formed by passing 
the formiate of ammonia, (NH 4 0+C 2 H0 3 ,) through 
a red hot porcelain tube, by which it is converted 
into this acid, (C 2 NH,) and water, (4HO.) The an- 
hydrous acid is a clear, limpid, inflammable fluid 
of the sp. gr. of .697. It boils at 80°, and con- 
geals at 5°. It has a penetrating, bitter taste, a very 
peculiar odour, and mixes freely with water, alcohol, 
and ether. It is a most powerful poison, and is 
rapidly decomposed by exposure to light. 

588. Metallic Cyanides. — Cyanogen forms a se- 
ries of true haloid salts with the metals, and so ener- 
getic is its affinity for some of them, that it will take 
palladium from all its other compounds, and that 
potassium, when heated in it, takes fire, combining 
with, but not decomposing the cyanogen. 

The cyanide of potassium is fusible and soluble, 
crystallizes in cubes, has a pungent, alkaline taste, 
and is highly poisonous. 

The bicyanide of mercury crystallizes in quadran- 
gular prisms, is colourless, inodorous, soluble in 



268 PRINCIPLES OF CHEMISTRY. 

water, has a disagreeable metallic taste, and is 
highly poisonous. When heated it is resolved into 
mercury and cyanogen. 

589. With sulphur, iron, and cobalt, cyanogen 
forms compounds which are, like itself, genuine salt 
radicals, and which form with hydrogen, acids, which 
are decomposed by metallic oxides, in the same man- 
ner as chlorohydric acid, thus forming genuine salts. 

590. Ferrocyanogen. — With iron, cyanogen forms 
two compounds; the constitution of the first, 
called ferrocyanogen, isFeCy 3 ; its symbol is Cfy, 
and its equivalent 107.17. It forms with hydro- 
gen a bibasic acid, the ferrocyanohydric acid, of 
which the formula is FeCy 3 +H 2 . The acid is a 
white, crystalline mass, the salts of which were ori- 
ginally called prussiates. Thus the yellow prussiate 
of potassa, is the basic ferrocyanide of potassium, 
the formula of which is K 2 Cfy. It is the yellow 
salt, prepared by calcining animal matters with 
potash, and is obtained in large, flat, quadrangular 
crystals, which contain 3 atoms of water. It is of a 
lemon yellow colour, and a slightly bitter taste. It 
forms double salts with the other ferrocyanides, and 
is much used as a test for iron. 

591. Ferridcyanogen. — The second compound 
of iron and cyanogen, is called ferridcyanogen; it is 
isomeric with the former, and its formula is Fe 2 Cy 6 ; 
its symbol, Cfdy, and its equivalent, 214.34. It unites 
with three atoms of hydrogen to form a tribasic 
acid, the ferridcyanohydric acid. The ferridcya- 
nide of potassium is the salt, known by the name of 
the red prussiate of potassa, and is formed by passing 
chlorine through a solution of yellow prussiate of 
potassa, till it ceases to give a precipitate of prussian 
blue, with persulphate of iron. It crystallizes in crys- 
tals of a deep red colour, and is valuable as a test for 
the metals. 

592. Prussian Blue. — There are several com- 



AMIDE. 269 

pounds of cyanogen and iron, prepared under the 
name of prussian blue. The common prussian blue 
is prepared by mixing together solutions of yellow 
prussiate of potash, and sesquisulphate of iron. It 
contains Cy 9 Fe 7 +Aq, and consists of one atom of 
ferridcyanide of iron, Fe 3 +Fe 2 Cy 6 , combined with 
one of the acid ferrocyanide of iron, FeH+FeCy 3 . 

A prussian blue, celebrated under the name of 
TurnbulPs blue, is prepared from the red prussiate 
of potassa; it yields Cy 6 Fe 5 , and is the basic ferrid- 
cyanide of iron, Fe 3 +Fe 2 Cy 6 . 

Prussian blue is insipid, insoluble, and inodorous, 
of an intensely pure, and beautiful blue colour. It 
loses its colour in the direct light of the sun, but re- 
covers it in the dark. 

593. The cyanide of cobalt, cobalt ocyanogen, 
Co 2 Cy 6 , and the bisulphuret of cyanogen — sirfpho- 
cyanogen, CyS 2 , are compound radicals, resembling 
ferrocyanogen, which form acids with hydrogen, 
and salts with the metals. 

The compounds of cyanogen with the salt radicals, 
resemble those of these elements with each other. 

594. Mellon. — Sulphocyanogen is decomposed 
by heat into sulphur, sulphocarbonic acid, and an 
insoluble yellow powder, the constitution of which 
is C 6 N 4 . This carburet of nitrogen has received 
the name of mellon. It forms an acid with hydro- 
gen, and haloid salts, and yields by the action of 
reagents, various singular and complicated products, 
the constitution, and relations of which, are imper- 
fectly understood. 



Section III. 

AMIDE. 

595. Almost the only product of organic decom- 
position which is destitute of carbon, is ammonia. 

23* 



270 PRINCIPLES OP CHEMISTRY. 

In order to explain the changes which this substance 
undergoes, the existence of a hypothetical radical, 
called amide, of which the formula is NH 2 , has 
been assumed. 

596. Jlmmonia. — Ammonia is a constant and 
copious product of the putrefaction of organic bodies 
containing nitrogen. A salt known, and highly 
prized, from remote ages, received its name of sal 
ammoniac from the temple of Jupiter Ammon, near 
which it was found as a natural product. When 
this salt is mixed with caustic lime in a state of fine 
powder, and subjected to heat, a gas of a very pun- 
gent and penetrating odour, which powerfully irri- 
tates the eyes and nostrils, is evolved. The same 
gas is produced during the destructive distillation of 
animal matters, especially of bones, and being fre- 
quently obtained from the horns of the deer, its so- 
lution in water was long known by the name of 
spirits of hartshorn. It is an invisible gas which 
is liquefied beneath a pressure of 6§ atmospheres; 
its sp. gr. is .5898. It extinguishes burning bodies; 
the flame of a taper before going out is somewhat 
enlarged, and assumes a yellow colour; and a small 
jet of the gas burns in oxygen gas. 

597. Ammoniacal gas, according to Kane, has no 
action on vegetable colours, when perfectly dry, but 
if damp, it is powerfully alkaline. It has a strong 
affinity for water, which absorbs 780 times its vo- 
lume. The sp. gr. of a solution containing 690 times 
its volume is .875. The concentrated solution is 
prepared by decomposing chlorohydrate of ammo- 
nia by means of lime, and passing the disengaged 
gas through water, kept cool by surrounding the 
vessel with ice or wet cloths. Owing to its strong 
affinity for water., ammonia must always be collected 
over mercury. A piece of ice introduced into a 
vessel of this gas is instantly liquefied, and the gas 
as instantly absorbed. Ammonia has all the proper- 



AMMONIUM. 27 i 

ties of an alkali; it has an acrid taste, stains turme- 
ric paper of a brown colour, and is a powerful base, 
neutralizing the strongest acids. 

598. When a succession of electric sparks is passed 
through this gas, it is entirely decomposed; its vo- 
lume is doubled, and the resulting gases are three 
volumes of hydrogen, and one of nitrogen; its for- 
mula may therefore be given as NH 3 , and its equiva- 
lent, as 17.15. 

599. A weak solution of ammonia is decomposed 
by the secondary action of the voltaic pile; hydro- 
gen, from the decomposed water, being evolved at the 
negative, and nitrogen at the positive electrode. But 
if a portion of mercury form the negative electrode, 
no hydrogen is evolved, and the mercury is rapidly 
converted into a light porous substance, having the 
lustre and all the characters of an amalgam. So un- 
stable however is its constitution that if the current 
of electricity ceases, it is at once resolved into mer- 
cury, two volumes of ammoniacal gas, and one vo- 
lume of hydrogen. This decomposition is retarded 
by subjecting the amalgam to an intense cold before 
discontinuing the current. It may be preserved at 
zero, and is then found to crystallize in cubes, and 
to retain its metallic character. (Kane.) 

600. Jlmrnonium. — This amalgam must be re- 
garded as a compound of mercury, and of these gases, 
in the above proportions; and as the metals do not 
form compounds possessing metallic properties, with 
any other bodies than metals, the existence of a 
compound metal which has not yet been insulated, 
and which must be represented by NH 4 , is inferred. 
To this suppositious metal, Berzelius gives the name 
of avimonium. He supposes the volatile alkali to 
be the protoxide of ammonium, NH 4 +0, which is 
resolved by decomposition into one atom of water, 
x>ne of nitrogen, and three of hydrogen. This the- 



272 PRINCIPLES OF CHEMISTRY. 

ory places ammonia in the class of metallic protox- 
ides, to which the other alkalies, potassa, soda, and 
lilhia, belong, and is supported by many strong 
analogies. 

601. If this view be correct, it is evident that the 
protoxide of ammonium is the hydrate of ammonia; 
such is in fact the constitution of the salts of ammo- 
nia with the oxygen acids, of which an atom of 
water is an essentiaL element. 

The real nature of ammonia is a question of much 
interest and difficulty, and there are other facts which 
seem to favour a theory that connects it with the 
series of organic radicals above described. 

602. Amide. — When the oxalate of ammonia, 
(C 2 3 +NH 4 0) is heated, two atoms of water are 
disengaged, and a new substance, called oxamide, of 
which the formula is C 2 2 +NH 2 , is evolved So, 
likewise, chloride of mercury, (HgCl), and ammo- 
nia, (NH 3 ), produce chlorohydric acid, (HC1), and 
Hg, NH 2 . One atom of bichloride of platinum, and 
two of ammonia, produce 2HC1, and P1+2NH 2 . It 
is evident, therefore, that the third atom of hydrogen 
is not so closely united to the nitrogen, as the re- 
maining two; for the former is separated by the or- 
dinary chemical reactions, but the latter are not dis- 
engaged till the ammonia is resolved into its ultimate 
elements. It is hence concluded, that the real base 
of ammonia is this bihydroguret of nitrogen, which 
has received the name of amide, and of which the 
formula is NH 2 , the symbol, Ad, and the number, 
16.15. 

603. Although amide has not been insulated, it 
forms compounds with many of the metals and or- 
ganic radicals. When potassium is heated in dry 
ammoniacal gas, an atom of water is disengaged, 
and a fusible olive green solid remains, which is 
K, NH 2 , the amidide of potassium. The amidide 



DOUBLE NATURE OF AMMONIA. 273 

of mercury forms compounds with the mercurial 
chlorides, oxides, and salts, some of which have been 
long known and used in the practice of medicine. 
The white precipitate of the shops is the chloride and 
amidide of mercury; HgAd+HgCl. 

604. Amide combines with many of the organic 
radicals: its combination with benzule is called ben- 
zamide, and with carbonic oxide, oxamide. These 
compounds differ, in their ultimate analysis, from the 
benzoate and oxalate of ammonia, in yielding one 
atom less of water; but they are entirely destitute 
of saline properties, and are formed by the same 
change which chlorohydric acid undergoes, when it 
acts upon a metallic oxide; that is to say, the am- 
monia parts with its third atom of hydrogen, and 
benzoic and oxalic acids, with that atom of oxygen 
which constitutes them acids, thus forming one atom 
of the new compound, and one of water. 

Oxamide is a tasteless, inodorous, snow-white 
crystalline powder, almost insoluble in cold water, 
ether, and alcohol, and readily converted into oxa- 
late of ammonia by acids or alkalies, and by heat. 

605. Double nature of Ammonia, — The pheno- 
mena which ammonia presents, are in one respect 
of a very remarkable, and of what may be called a 
dimorphous character. When it combines with oxy- 
gen acids, its salts, as has been stated, contain an 
atom of water as an essential element, and are iso- 
morphous with the corresponding salts of potassium ; 
and it exhibits in this respect all the properties of 
a highly basic metallic protoxide, as strongly as any 
of the class; and we are led to infer, that in these 
cases it is the hydrated protoxide of ammonium 
which enters into combination. 

606. On the other hand, ammonia exhibits prop- 
erties which bring it into close affinity with water, 
and which remove it entirely from the class of alka- 
lies, with which, in other respects, it is so closely 
connected. 



274 PRINCIPLES OF CHEMISTRY. 

Many of the metallic salts copiously absorb dry 
ammoniacal gas, and form definite compounds, in 
which ammonia appears to act the part of basic 
water, or water of crystallization. Thus dry sul- 
phate of zinc is converted into a bulky white pow- 
der, perfectly soluble in water, and consisting of 
2 (ZnO, S0 3 )+5AdH. The sulphates of copper, of 
nickel, of cobalt, and of cadmium, combine with two 
and a half or three equivalents of ammonia, and form 
soluble compounds. From some of these the ammo- 
nia escapes by mere exposure to the air; in some 
the salt may be sublimed without change, while in 
others one portion of the ammonia is more strongly 
retained than the rest. In these cases, it seems prob- 
able that ammonia acts as the amidide of hydro- 
gen, analogous to the protoxide of hydrogen, and 
not as the protoxide of ammonium. 

607. This double nature of ammonia is shown by 
the decomposition which takes place, when an excess 
of ammonia is added to a strong, hot solution of 
nitrate of copper. The ammoniacal nitrate of cop- 
per crystallizes in fine, purple, rhombic octohedrons. 
This salt deflagrates violently when heated to the 
melting point, and appears to consist of nitrate of 
ammonia, NH 4 ,N0 6 , and of the amidide of copper, 
Cu Ad; one portion of the ammonia being resolved 
into amide, and the other into ammonium. 

608. Salts of Ammonium. — Of the oxygen salts 
of ammonia, the nitrate is principally used for the 
preparation of protoxide of nitrogen. The sulphate 
is obtained from the liquid products of the distillation 
of coal, in making coal gas — and is used for the prep- 
aration of the chloride of ammonium — the crude 
sal ammoniac of commerce. 

The phosphate of ammonia and magnesia is much 
used as a flux in blow pipe experiments, and was 
formerly called microcosmic salt. 

The oxalate of ammonia is much used as a test 
of the presence of lime. 



FULMINATING COMPOUNDS WITH THE METALS. 275 

With carbonic acid, ammonia forms a neutral an- 
hydrous carbonate, NH 3 C0 2 , and a bicarbonate. The 
constitution of the latter is NH 4 0, C0 2 +H0, C0 2 . 
By the union of these in various proportions, several 
complex varieties of the carbonate are formed. 

609. Amide and the Salt Radicals. — When am- 
monia is made to act on the salt radicals, and on 
some of the metallic oxides, certain compounds are 
formed of so unstable a constitution, that the slightest 
molecular agitation is sufficient to decompose them, 
with violent detonation. The extreme danger of 
examining and handling these preparations, has pre- 
vented their accurate analysis, but from the simi- 
larity of their properties, it is probable that the 
ammonia used in their preparation, undergoes the 
same change in all, and exists in the condition of 
amide, feebly combined with a salt radical, or a me- 
tallic oxide. 

As traces of sal ammoniac are perceived when it is 
decomposed, it must contain hydrogen; and it is 
highly probable that it is a chloride of amide. 

610. Terchloride of Nitrogen. — This compound 
is prepared by exposing a solution containing a 16th 
part of chlorohydrate of ammonia, to the action of 
chlorine gas. Minute yellow globules of the chlo- 
ride soon begin to collect at the bottom. It is one 
of the most explosive compounds known. Its sp. gr. 
is 1.653. It does not congeal at zero of Fahrenheit; 
it may be distilled at 160°, and explodes with great 
violence at 212°, as well as by the mere contact of 
combustible substances. 

With iodine and bromine, ammonia forms similar 
compounds; that with iodine is a brown powder, 
which explodes under water by friction. 

611. Fulminating Compounds with the Metals. 
When the fresh prepared oxides of silver, gold, pla- 
tinum, mercury, and copper, are digested in water 
of ammonia, an insoluble powder is formed, which 



276 PRINCIPLES OF CHEMISTRY. 

detonates with friction; and in the case of silver, and 
gold, with extreme violence. The composition of 
these bodies is uncertain. They yield hydrogen and 
nitrogen in the proportions to form ammonia, but it 
is evident that so stable a compound as ammonia, 
cannot, as sach, enter into their composition. 



Section IV. 

THE ORGANIC ALKALIES. 

612. The researches in organic chemistry have 
brought to light a multitude of proximate principles, 
which are secreted during the life of the plant or 
animal, and which are, in most cases, peculiar to the 
species or genus in which they exist. The most 
remarkable of these proximate principles is a series 
of organic alkalies, to which the plants that contain 
them owe their active medicinal properties. They 
all contain nitrogen, and all act as bases, neutrali- 
zing the strongest acids, and forming with them neu- 
tral crystalline salts, retaining the peculiar power 
over the animal system which the base' itself pos- 
sesses. The most remarkable of these alkalies are 
those found in the cinchonas, in the poppy, and the 
nux vomica. These alkalies exist naturally in com- 
bination with organic acids, peculiar, like them- 
selves, to the plant. 

613. Three distinct, but closely allied alkalies are 
obtained from the cinchonas. 

Cinchonia, of which the formula is NC 20 H 12 0, 
exists in the red and gray bark; quinia or quinine, 
NC 20 H 12 O 2 ,in the yellow bark; and aricina,NC 20 
H 12 3 , in the aricara bark, a tree closely allied to 
cinchona. These alkalies are all soluble in alcohol, 
and nearly or altogether insoluble in cold water; 
their taste is intensely bitter, and they crystallize in 
brilliant needles or prisms. They appear to be the 



INDIGO. 277 

principles to which peruvian bark owes its febrifuge 
virtues, and the disulphate of quinine, Qu 2 S0 3 +8 Aq, 
is extensively manufactured for medicinal purposes. 

614. Morphia. — The narcotic virtues of opium 
are due to various alkaline principles, which have 
been obtained from it by the action of acids, and of 
alcohol. It seems probable that some of these are 
secondary products, and that they do not exist in the 
plant itself. The most important of these alkalies is 
morphia, the chief narcotic principle of the poppy. 
Morphia is almost insoluble in cold water, but dis- 
solves freely in alcohol. Its solution is intensely 
bitter to the taste, and strongly alkaline. Morphia 
neutralizes the strongest acids, and forms soluble 
crystalline salts. It colours nitric acid red, forms a 
copious white precipitate with tannic acid, and a 
rich blue liquid with sesquichloride of iron. Its 
formula is NC 35 H 20 O 6 . Its chlorohydrate, acetate, 
and sulphate, are much used in medicine as substi- 
tutes for opium. 

615. Strychnia. — The nuts of the various species 
of the genus strychnos, are intensely poisonous, and 
owe their power to two alkalies, strychnia and bru- 
cia. Strychnia is the best known of these; it has 
an intensely bitter, somewhat metallic taste, and ren- 
ders 700,000 parts of water strongly bitter. It is 
nearly insoluble in ether, absolute alcohol, and water, 
but dissolves readily in spirits of wine. It forms 
soluble crystalline salts, and is one of the most in- 
tense poisons known to us. Its formula is N 2 C 4 
H 22 4 . 



'44 



Section V. 

COLOURING MATTERS. 

616. Indigo. — One of the most remarkable nitro- 
genous products of vegetation, is indigo. It is se- 

24 



278 PRINCIPLES OF CHEMISTRY. 

creted in the cellular tissue of various plants, and so 
long as the tissue remains perfect, it is colourless. 
But when the leaves begin to wither, the indigo 
absorbs oxygen, and acquires a blue colour. It is 
prepared by placing the leaves in large vats, in 
which they undergo a species of fermentation, and 
yield a yellow liquor, w r hich contains the indigo. 
This is mixed with lime water, and the indigo 
slowly absorbs oxygen, becoming blue and insolu- 
ble. As thus prepared, indigo is a mixture of vari- 
ous bodies, from which it may be obtained by sub- 
limation, as a rich purple vapour, which condenses 
into brilliant, purple, prismatic crystals, of a metallic 
lustre. The formula of this pure indigo is, NC 16 H 5 
2 . By the action of deoxidizing agents, indigo 
loses its blue colour, and becomes soluble in alkaline 
solutions. This colourless indigo is a compound of 
blue indigo with an atom of hydrogen, and it re- 
covers its blue colour and insolubility, by the absorp- 
tion of an atom of oxygen from the air. It may be 
prepared by mixing 1| parts of indigo, 2\ of slaked 
lime, and 2 of sulphate of iron, with 60 of water, in 
an air tight vessel. The oxide of iron decomposes 
the water, the hydrogen of which combines with 
the indigo, rendering it colourless and soluble. Chlo- 
rohydric acid precipitates the white indigo from this 
clear solution, as a crystalline white powder. When 
cloths are dipped in this solution, the colourless in- 
digo is precipitated in the fibre, and regains its blue 
colour in the air. 

617. Indigo dissolves in sulphuric acid; and the 
solution retains the brilliant colour of the indigo, and 
is much used in dying by the name of Saxon blue. 
There appear to be two acid sulphates thus formed, 
one of which, called the sulphopurpuric acid, con- 
tains two atoms of each of its elements; and the 
other, the sulphindylic acid, is a bisulphate of indi- 



MORDANTS. 279 

go; both of these acids form neutral salts with a sin- 
gle atom of alkali. 

618. Carbazotic Acid, — By the action of acids 
and alkalies, indigo is resolved into several new 
compounds, the most important of which is the 
picric, or carbazotic acid. This acid is formed by 
the action of nitric acid on indigo ; it crystallizes 
in brillant yellow prisms, explodes by the action of 
heat, and forms detonating salts. Its taste is in- 
tensely bitter, and it forms an almost insoluble salt 
with potassa, which renders it one of the most deli- 
cate tests of that alkali. The formula of carbazotic 
acidisC 14 H 4 N0 9 +Aq. 

619. Red Colouring Matters. — The principal red 
dyes are those obtained from the cochineal insect, 
brazil wood, log-wood, the roots of the madder, the 
flowers of the carthamus, and the resin of the lac in- 
sect. The colouring matter of all these substances is 
obtained in a solid form by dissolving them in a solu- 
tion of alum, and precipitating the alumina by means 
of an alkali. The colouring matter falls in combi- 
nation with it, and the precipitate when dried is 
known by the name of lake. These lakes are also 
obtained by means of chloride of tin, which forms 
richly coloured solutions, from which the colouring 
matter may be precipitated in combination with 
oxide of tin, by an alkali. 

620. All the tints of the dyers may be produced 
by the combination of four principal colours, black, 
red, yellow, and blue. 

The chief yellow dyes are the quercitron, or black 
oak bark, turmeric, fustic, and saffron. Black is 
produced by the pergallate and pertannate of iron. 

621. Mordants. — Many of these colouring mat- 
ters have so strong an affinity for wool, silk, and 
flaxen, and cotton fibre, that they do not wash out 
from the cloths that have been died with them. 



280 PRINCIPLES OF CHEMISTRY. 

Others again have so little affinity for organic 
fibre, that they readily wash out. These colours 
can be made fast colours, by first dipping the ma- 
terial to be dyed, in a solution of alum, or some 
other salt, the base of which has an affinity both for 
the fibre and colouring matter, which are thus made 
to enter into a permanent combination. A salt of 
this kind is called a mordant or basis; colours which 
adhere to cloth without a basis, are called fast or 
substantive colours; those which require one, ad- 
jective colours. 



Section VI. 

NEUTRAL NITROGENOUS COMPOUNDS. 

A few colourless substances, possessing neither 
acid nor basic properties, are here grouped together. 

622. Asparagine.— This proximate principle is 
contained in asparagus, the marsh mallow, and 
liquorice. It crystallizes in a rectangular octahe- 
dron, and in hexahedral prisms, is inodorous, and 
has a slightly cool, nauseous taste. It is soluble in 
water, but insoluble in ether and alcohol, and has 
no affinity for either acids or alkalies. Asparagine is 
resolved into a peculiar acid, termed the aspartic 
acid, and into ammonia, by being boiled with hy- 
drated oxide of lead or magnesia, and it bears the 
same relation to this acid, that urea bears to cyanic 
acid. Anhydrous asparagine consists of C 8 H 8 N 3 6 , 
and aspartic acid of C 8 H 5 N 1 6 , so that the former 
is isomeric with aspartate of ammonia, C 8 H 5 N 1 6 
+H 3 N 1 , yet alkalies do not evolve ammonia, nor 
acids, aspartic acid, from asparagin. Crystallized 
asparagin, contains two atoms of water. 

623. Caffeine, Theine. — One of the most remark- 



BLOOD. 281 

able coincidences, which the researches in organic 
chemistry have brought to light, is the absolute 
identity of the active principle of the tea plant, and 
the coffee berry; two plants, which, although na- 
tives of countries remote from each other, and 
brought into use by nations of the most opposite 
habits, have become, from a sort of instinctive relish, 
the favourite beverage, and almost a necessary of 
life, with civilized man in all climates. Caffeine 
crystallizes in long brilliant needles, of a rich satiny 
lustre. It has a purely bitter taste, is soluble in 
water, has neither acid nor basic reaction, and con- 
tains more nitrogen than any other vegetable pro- 
duct. Its formula is N 2 C 8 H 6 2 +Aq. 

A nitrogenous resinous product, called piperine,is 
extracted from the various species of pepper. Its 
formula is NC 34 H 19 9 . 



Section VII. 

THE ANIMAL FLUIDS. 

624. The principal elements of the animal fluids 
have been stated to be fibrine, caseine, and albu- 
men. They form the materials from which the tis- 
sues and skeleton of the living being are supplied 
with new matter. These, in conjunction with gela- 
tine, and various earthy and alkaline salts, compose 
the animal structure. 

625. Blood. — If fresh drawn blood be made to 
trickle over a plate of silver heated to 140°, it dries 
to a red, glossy, brittle mass, which yields by analy- 
sis, precisely the same proportions of nitrogen and 
hydrogen, carbon and oxygen, as proteine, so that the 
blood contains in a liquid form the identical con- 
stituents of flesh and cellular tissue. The specific 
gravity of blood is 1.055. When it is allowed to rest 

24* 



282 PRINCIPLES OP CHEMISTRY. 

it separates into a yellow liquid, called the serum, and 
a gelatinous red mass, called the clot or cruor. If 
it be examined under a microscope, blood will be 
found to consist of a multitude of red globules, float- 
ing in a nearly colourless liquor. These globules 
are circular or oval flattened discs, varying in differ- 
ent animals from -g oVo t0 reVo °f an * nc h m diameter. 
They consist of a central colourless albuminous nu- 
cleus, surrounded by a membrane, which is coloured 
red by a peculiar principle, called hsematosine. These 
red globules, along with the fibrine and a large por- 
tion of the albumen, form the coagulated mass, called 
the cruor. Lecanu found the blood to contain 13.3 
per cent, of blood globules, .21 of fibrine, 6.51 of al- 
bumen,^ of fatty and extractive matters, 1.05 of al- 
kaline and earthy salts, and 78.26 of water and loss. 
Haematosine is a dark brown, tasteless, inodorous 
mass, which is insoluble in ether, alcohol, and water, 
but which forms blood red solutions with alkalies, 
and a rich permanent dye with bichloride of mercury. 
It constitutes but 4 or 5 percent, of the red globules; 
and its formula, according to Mulder, is C 44 H 22 
N 3 6 Fe. 

626. Milk. — This fluid, in addition to caseine, con- 
tains sugar and oils, which like the analogous vege- 
table secretions, are destitute of nitrogen. The caseine 
exists in milk in two conditions, soluble and insolu- 
ble; the former remains in the milk, the latter sepa- 
rates with the cream. By contact with caseine, sugar 
of milk is converted into lactic acid. Berzelius found 
cream from cow's milk to consist of 4.5 per cent, of 
butter, 3.5 of caseine, and 92 of whey. Skimmed 
milk contains 2.6 per cent, of caseine and butter, 3.5 
of sugar of milk, .6 of extractive and lactic acid, .17 
chloride of potassium, .255 of earthy and alkaline 
phosphates, and 92.875 of water. 

627. Mucus and Gastric Juice. — The internal 
surface of the alimentary canal, is kept constantly 



BILE. 



283 



moist, by a thick tenacious mucus, closely resembling 
the solution of cerasine, but containing nitrogen. 
When any substance is introduced into the stomach, 
there is copiously secreted, in addition to the mucus, 
a colourless pale yellow liquid called the gastric 
juice. This fluid contains about two per cent, of 
common salt and sal ammoniac, and a portion of free 
chlorohydric acid, and possesses the remarkable 
property of softening the food, and converting it into 
an uniform gray pulp, called chyme, from which the 
absorbent vessels take up the nutritious portions. 
It owes this property to the presence of an organic 
principle, called pepsine, which excites, in the food 
that enters the stomach, a true fermentation, convert- 
ing it into chyme, by communicating to it the molec- 
ular change which its own particles are undergoing, 
in the same manner as ordinary ferment gives rise 
to the changes which convert sugar into alcohol. 

628. Bile. — As soon asthe chyme has passed from 
the stomach, it receives the addition of bile, a liquid 
which distils drop by drop from the gall bladder into 
the intestinal canal, and which converts the chyme 
into chyle. This is an opaque, white, milky fluid 
which contains the same elements as blood, and is 
collected from the innumerable vessels, at the ex- 
tremity of which it is taken up from the intestines, 
and poured into the venous blood before the latter 
returns to the heart. The bile, which thus converts 
the digested food into chyle, is secreted by the liver 
from the venous blood which passes through it in 
the course of circulation. It is a fluid of a greenish 
yellow colour, which contains 91.5 per cent, of water, 
united with resins, a fatty acid, soda and common 
salt. The principal element of bile is the choleic 
acid, which is a bitter, yellowish white, brittle mass, 
soluble in ether and alcohol, and forming soaps with 
alkalies, It exists in the bile in combination with 



284 PRINCIPLES OF CHEMISTRY. 

soda, and its formula, according to Liebig,is C 76 N 2 

H 66 22- 

629. Urine. — As it is the office of the liver to ab- 
stract from the venous blood, in the shape of bile, all 
excess of carbon which it contains, so it is the func- 
tion of the kidneys, to separate from the arterial 
blood, all the products which are rendered unfit for 
circulation by containing an excess of nitrogen. 
None of the animal fluids is subject to such changes 
in its constitution, from age and disease, as the urine. 
In a healthy person it contains 93.3 per cent, of 
water, 3 of urea, 1.7 of lactic acid, .1 of uric acid, 
and nearly 2 per cent, of alkaline and earthy phos- 
phates and sulphates, and common salt. 

630. Urea. — Urea is obtained in brilliant white 
quadrangular prisms. It is an inodorous, neutral 
substance, of a nitrous taste, soluble in water, and 
producing great cold during its solution. Its formula 
is N 2 C 2 H 4 2 . The solution of urea in pure water 
continues long unaltered; but if any ferment is pre- 
sent, a change of constitution takes place, it appro- 
priates to itself four atoms of water, and is converted 
into 2 atoms of carbonate of ammonia; N 2 C 2 H 4 
2 +H 4 4 , becoming 2(C0 2 +NH 4 0). Urea is 
isomeric with cyanate of ammonia, NC 2 0+NH 4 0; 
and may be artificially prepared by mixing solutions 
of cyanate of silver, and chlorohydrate of ammonia. 
Chloride of silver is precipitated, the remaining solu- 
tion does not yield cyanic acid with acids, nor am- 
monia with alkalies, but crystallizes into quadrangu- 
lar prisms identical with urea. 

631. Uric Acid. — This acid is found in the urine 
of carnivorous animals, and in the dry white excre- 
ment of serpents. The latter consists chiefly of urate 
of ammonia. Pure uric acid is white, tasteless, ino- 
dorous, and very sparingly soluble in water. It red- 
dens litmus paper and forms crystalline salts. Its 



URIC ACID. 285 

formula is N 4 C 10 H 4 6 . The bony concretions, 
which are formed in the joints in gouty patients, con- 
sist of urate of soda. 

By the action of nitric acid, uric acid undergoes a 
series of very remarkable changes, giving rise to 
compounds of great interest in a theoretical point of 
view, and some of them possessing singular beauty 
of colour. 



286 



PART THIRD. 

THE HISTORY OF CHEMICAL PHILOSOPHY. 



CHAPTER I. 

THE CHEMICAL KNOWLEDGE OF THE ANCIENTS. 

632. Although the science of chemistry bears 
every mark of being upon the eve of great changes, 
which will separate its future from its present, by 
even a wider interval, than separates its present from 
its past conditon, there is perhaps no example in the 
whole range of science, of clearly demonstrated doc- 
trines, more contradictory in appearance to all our 
ordinary conceptions, than are to be found in its do- 
main. The present is separated from the past, the 
scientific view, from the popular notions, by so wide 
a gulf, that the study of chemistry would be defi- 
cient in some of its most instructive lessons, if we 
were to omit the history of its rise and progress. 

633. This science being the developement of the 
laws which govern the mutual action of bodies, and 
the changes consequent upon their intermixture, the 
elements of a rude chemistry must have existed in 
the earliest ages, as soon as men began to explore 
the material world around them, and to apply to 
their own use the qualities which they thus disco- 
vered. We must suppose that many of the early 



CHEMICAL PHILOSOPHY. 287 

discoveries were the result of accidental combina- 
tions ; and yet the knowledge which the fathers of 
mankind acquired, and the arts they practised, seem 
more like the results of a wisely directed instinct, 
which is but another name for the inspiration of su- 
perior power, than the slow and irregular advances 
of blind chance and necessity; so greatly are they 
superior to the arts known to those branches of our 
race, who having lost the traces of that original 
knowledge, and sunk into a barbarous ignorance, 
have been compelled to toil up the steep and almost 
inaccessible paths, which lead back to industry and 
civilization. 

634. It is difficult, perhaps impossible, to ascer- 
tain the exact extent to which the ancients practised 
the chemical arts. Of chemical theory they were 
absolutely ignorant ; but they could not fail to become 
acquainted with the more common and useful metals, 
to discover many of the salts which exist in a state 
of nature, and to apply their properties in some of 
the various processes and manufactures with which 
they were acquainted. 

635. We cannot, in many cases, determine the 
substances designated by names which we now ap- 
ply to familiar and well known objects; objects, 
which, we are apt to think, have always been so 
called, while in fact the names are of far greater an- 
tiquity than the discovery of the substances them- 
selves, and have been variously applied according to 
the state of the arts and civilization. In the an- 
cient languages, moreover, there are many terms for 
which we have no modern equivalents, or of which 
the only translation that can be given is conjectural; 
so that at every stage of the inquiry into the arts 
and knowledge of the ancients we meet with doubts 
and difficulties not easily to be resolved. 

636. Seven metals were known to the Greeks and 
Romans, viz. gold, silver, copper, iron, lead, tin, and 



288 HISTORY OF 

mercury. Of these, the first five appear to have 
been known to mankind in the earliest ages. There 
seems little doubt that gold was the first of these 
metals which attracted the attention of man. Being 
found in masses of sufficient magnitude to exhibit 
its properties of fusibility, malleability, and ductility; 
its beauty of colour, its brilliancy, and unalterability 
by the air and by fire, rendered it an object of uni- 
versal admiration and eager desire. Its discovery 
must be regarded as an era in the history of the arts, 
for it possesses properties so peculiar, and so useful, 
so different from most of the rude materials which 
met their gaze, that men must have had their curiosi- 
ty strongly excited, to learn whether there were any 
other substances possessing similar qualities of fusi- 
bility, ductility, and malleability. The discovery of 
silver, of copper, and of iron, metals which are occa- 
sionally found native, was probably the first fruits of 
this search ; if indeed it was not accidental, and con- 
temporaneous with that of gold, for we know that 
these metals were in use before the flood. It is not 
an unlikely conjecture, that the accidental presence 
of some of the ores of these metals in the vessels 
in which the operation of melting was performed, 
or in the ground where a great fire had been kindled, 
led the way to the knowledge, that there were stony 
substances from which these precious materials could 
be extracted. The presence of native silver and 
copper in frequent association with stones of certain 
characters, was a sufficient indication of their exist- 
ence in these ores. As no mineral substance was 
more likely to excite their attention from its weight 
and metallic lustre, or would sooner reward their 
labour by yielding up its metal, than galena, it is a 
very natural conjecture, that the discovery of lead 
was one of the first fruits of these rude investiga- 
tions. The frequent union of the ores of iron with 
those of copper, would soon lead to the discovery of 



CHEMICAL PHILOSOPHY. 



289 



the art of obtaining that metal, if its accidental pro- 
duction by fire in the way pointed out, be not more 
probable. 

637. Gold and silver were melted, and cast, and 
hammered, into various forms; and were also beaten 
into thin plates, which were used in covering wood 
and other materials. The extreme thinness which 
has been given to those metals by modern goldbeat- 
ers, is, however, an art of recent date. 

638. The Egyptians, before the time of Moses, 
knew the process for hardening iron, so as to render 
it fit for axes and other cutting tools. Five hundred 
years later, however, the use of copper for these 
purposes still continued among the Greeks, who had 
no other swords, at the time of the Trojan war, than 
those made of copper hardened by fire. 

They afterwards learned the property which iron 
possesses, of being welded, and knew the art of con- 
verting that metal into steel. But it is a remarkable 
proof of the looseness of their habits of observation, 
that both the Greeks and Romans attributed the 
hardening of soft iron by sudden cooling, to a pecu- 
liar property of certain waters, which acquired there- 
by extraordinary celebrity. Like most of the arts 
and learning of the age, the knowledge of iron was 
brought from the East, and the word Chalybs was 
the name of a tribe on the Euxine, from whom the 
Greeks learned the use of the metal, just as our term 
for all the finer kinds of pottery, is an acknowledgment 
that we derived the art of making them from the 
Chinese. 

639. The name Stannum, which we translate Tin, 
and which was, without doubt, subsequently applied 
by the ancients to that metal, appears to have origi- 
nally denoted an alloy of lead and silver, from which 
the art of separating the more precious metal was 
unknown. The tin of ancient commerce was pro- 
cured by the Phenicians from Spain and Britain, 

25 



290 HISTORY OF 

the inexhaustible mineral riches of the latter country 
having been thus early known. 

The ancients alloyed copper with lead and tin, and 
carried to great perfection the art of casting statues 
of bronze, which was an alloy of these metals in 
various proportions. 

640. Although ignorant of the existence of zinc 
as a peculiar metal, they were well acquainted with 
the alloy of that metal and copper, and with the ore 
of zinc, called calamine, which was used then, as it 
is now, for obtaining brass. 

641. Lead was in common use among the Egyp- 
tians in the time of Moses. Like tin, it was chiefly 
furnished by the Phenicians, who obtained it from 
Spain and Britain. It was beaten into thin sheets, 
as at present, and was cast into pipes for the convey- 
ance of water. 

642. Mercury was found in the mines in its native 
state, and was also obtained from cinnabar. It is 
not mentioned by Moses, or by Herodotus, so that 
its discovery is probably of later date than that of 
the other metals, of which we have been speaking. 
The ancients knew that it dissolved gold and silver, 
lead, copper, and tin, and applied it to the purpose 
of gilding, in the same manner as is now done. 

643. It seems probable that Bismuth was occa- 
sionally seen by the ancients, but that it was not dis- 
tinguished by them from tin or lead. 

644. The sulphuret of antimony was used by the 
Asiatics, as it is to this day, for blackening the eye 
brows, and what is not a little singular, the term 
alcohol, now used only for spirits of wine, was origi- 
nally applied to this powder. The red and yellow 
sulphurets of arsenic were known as pigments. The 
black oxide of manganese was employed, as now, 
by the ancient potters, without its being known, 
however, that it contained a distinct metal. 

645. The ancients were acquainted with many 



CHEMICAL PHILOSOPHY. 291 

other pigments prepared from the metals, such as 
red and white lead, cinnabar, the ochres, and the 
blue and green carbonates of copper. They were 
acquainted with alum, and copperas, and knew their 
use in dying. The Egyptians knew the art of calico 
printing, and the nature of mordants, for Pliny de- 
scribes with great clearness the process still employed 
in India for printing in colours. " There exists in 
Egypt," says he, " a wonderful method of dyeing. 
The white cloth is stained in various places, not with 
dye stuffs, but with substances which have the pro- 
perty of absorbing colours. These applications are 
not visible upon the cloth ; but when they are dipped 
into the hot caldron of the dye, they are drawn out, 
an instant after, dyed. The remarkable circumstance 
is, that though there be only one dye in the vat, 
yet different colours appear upon the cloth; nor can 
the colour be afterwards removed." — Plinii Hist: 
Nat. xxxv. 11. 

So great a degree of skill implies a considerable 
knowledge of dyeing materials, and of mordants. 

646. Nitre was discovered in India and China, 
and the explosive mixture which it forms with sul- 
phur and charcoal was known in the latter country 
before the Christian era, although it was not applied 
to the purposes of war. It is altogether uncertain 
when this salt was introduced into Europe, but the 
nitre of the Greeks and Romans was natron, the 
mineral alkali, and they knew nothing of the modern 
nitre. Natron was used by them in the manufacture 
of glass. 

647. This material was known to the ancient Egyp- 
tians, and was probably an accidental and often made 
discovery, for the chance to which it is attributed 
must often have happened. Some Phenician mer- 
chants, it is said, landing near Berytus in Syria, with 
a cargo of natron, and having nothing wherewith to 
support their kettles, while they were dressing their 



292 HISTORY OF 

food, took lumps of the natron for that purpose; the 
fire melted the salt, and fused it and the sand of the 
shore into glass. The Egyptians coloured their glass 
with various metallic oxides, and formed it into ves- 
sels, and vases, and beads. The principal use made 
of it by the Phenicians, was for plates to line the 
walls and ceilings of their apartments. 

648. The art of making soap was practised by the 
ancient Germans and Gauls, but was known neither 
to the Greeks nor Romans till the time of the Roman 
emperors, when soap came into use as a pomatum. 

The only acid known to the ancients, was the ace- 
tic, as obtained by fermentation. 

They manufactured stone and earthen ware, and 
porcelain of a fine quality. They knew the use of 
calcined plaister of Paris in taking moulds, and pre- 
pared a mortar which hardened under water. 

Wine was universally known, and the Egyptians 
made a fermented liquor of barley. Beer was the 
favourite national drink of the Gauls and Germans. 
There is, however, no evidence that the ancients 
had any knowledge of the art of distillation. 

649. Such seems to have been the amount of 
knowledge possessed by the ancients in these par- 
ticulars. That knowledge remained for a long time 
nearly stationary, and it was not till the conquests 
of the Saracens overturned the old, and laid the 
foundation of a new order of society, that it began 
to advance. These conquests, by infusing new vig- 
our into the decaying institutions of Europe, and 
mingling the learning of the east with that of the 
west, revivified industry and commerce, and created 
anew the chemic arts. 



CHEMICAL PHILOSOPHY. 293 

CHAPTER II. 

THE ALCHYMISTS. 

650. The Saracen caliphs of Bagdad and Spain, 
.were the great patrons and restorers of the learning 
of the middle. ages. The caliphs of Cordova, from 
the eighth to the tenth century, and more especially 
the three Abdalralimans, and Alhakem, carried the 
splendour of their monarchy to the highest pitch. 
They were probably the best and wisest sovereigns 
that ever sat on the throne of Spain. Alhakem 
established an academy at Cordova, which was for 
several years the most celebrated in the world. In 
the tenth century it contained a library of two hun- 
dred and eighty thousand volumes. In the twelfth 
century, there were no less than seventy public libra- 
ries in Mahometan Spain. Cordova produced one 
hundred and fifty authors, Almeria fifty-two, and 
Murcia sixty-two. 

The caliphate of Bagdad was the great centre of 
learning in the east, as that of Cordova was hi the 
west. In the middle of the eighth century, Alman- 
zor founded the celebrated school of Bagdad, which 
numbered at one time more than six thousand schol- 
ars, who thronged thither from all parts of the civil- 
ized world. He established public hospitals for the 
sick, and laboratories for the preparation of medi- 
cines. These institutions gradually fell into decay, 
but were resuscitated in the thirteenth century by 
Mostanser; and Haroun al Raschid, Almamon, and 
their successors, patronized science with a zeal and 
liberality not inferior to that which animated the 
monarchs of Cordova. 

Under the genial protection of these caliphs, learn- 
ing of every kind flourished. The Arabs eagerly 

25* 



294 HISTORY OF 

cultivated the Greek philosophy and mathematics, 
but the sciences to which they directed their prin- 
cipal attention, were those connected with the heal- 
ing art. We find accordingly that they laboured 
incessantly to discover the effects upon the human 
frame, not only of all the plants which gave promise 
of medicinal efficacy, but that they explored for this 
end, with the greatest eagerness, the almost unopened 
mine of chemistry. Every thing here was to be 
begun anew; the sensible properties of chemical 
substances, and the manner in which they acted 
upon each other, had to be examined; and the nov- 
elty of the research, and the inexhaustible field of 
observation which was thus opened, drew crowds of 
votaries into these hitherto untrodden paths. 

651. They went on for ages groping in the dark, 
pursuing their way, they knew not whither, follow- 
ing every accidental gleam of light, wasting the 
strength of giants, and the acuteness of the greatest 
genius, in barren and almost useless labours. Yet 
they were unconsciously preparing the soil for the 
rich harvest which their successors reaped, and it 
will well repay the curiosity of philosophical re- 
search, to trace the steps by which the science has 
advanced, from the ignorance of the Greeks and 
Romans, through the absurdities and follies of al- 
chemy, to the sober ^nd patient research which has 
led to the brilliant discoveries of our own times. 

652. The Arabians had brought from the east the 
idle hope of being able to transmute the common 
metals into gold. Snatching at the similarity of pro- 
perties of many of those bodies, they fancied that tin, 
and lead, and copper, only differed from silver and 
gold in the addition of some ingredients, which ren- 
dered them less ductile and unalterable, and that 
there must be some means of separating the perfect 
metals from the dross and impurities that thus de- 
based them. 



CHEMICAL PHILOSOPHY. 295 

The success which attended their rude attempts 
in the healing art, led them to suppose that behind 
the curtain which veiled the secrets of nature, must 
be concealed remedies of greater and of universal 
power, able to drive pain, and disease, and death, 
from the earth. 

These vain expectations set in motion the two 
most powerful springs of action, the love of life, and 
the love of wealth, which impelled men in the 
search after new processes and combinations in chem- 
istry, with a zeal and devotion which could not 
probably have been supplied by any other motives. 

653. The writings of Geber are the earliest re- 
cords, now extant, of the progress which chemical 
knowledge had made between the Christian era and 
the middle ages. Geber was the assumed name of 
a native of Harran in Mesopotamia, who lived in the 
eighth century, and of whose personal history little 
or nothing is known. He was acquainted with me- 
tallic arsenic, in addition to the metals known to the 
ancients, and he regarded them all as compounds of 
mercury and sulphur. Of these gold and silver are 
perfect metals: gold consists of the most subtile sub- 
stance of mercury, as is proved by the ease with 
which the latter metal dissolves it; for mercury can 
dissolve nothing that is not of its own nature. Sil- 
ver, like gold, consists of much mercury with little 
sulphur; but its sulphur is white, while that of gold 
is red. The other metals were composed of earthy 
mercury and fixed sulphur; and they were all ca- 
pable of being converted into gold and silver by 
altering the nature and proportions of their sulphur 
and mercury. This change could be effected by the 
philosopher's stone, or the medicine, as he more 
commonly called it. 

Geber was acquainted with the process of distilla- 
tion, by which he purified vinegar, and he applied 
the term spirit, to sulphur, arsenic, and other volatile 



296 HISTORY OF 

solids. He is the first writer who gives an account 
of nitre, and he prepared what he called dissolving 
water, by subjecting to distillation a mixture of sul- 
phate of iron, nitre, and alum. He noticed the red 
fumes which are disengaged in the process, and used 
the liquid for dissolving silver. He was acquainted 
with crude sal ammoniac, and used its solution in 
his dissolving water for liquefying gold. He was 
acquainted with potash, soda, and alum; and by 
exposing the latter to a red heat in a glass retort, he 
obtained a weak sulphuric acid, which he preserved 
as a valuable menstruum. Geber mentions cop- 
peras, the sulphate of iron, which, as well as alum 
and nitre, he purified by solution and recrystalliza- 
tion. He made corrosive sublimate, cinnabar, and 
red precipitate ; he prepared precipitated sulphur by 
dissolving sulphur in caustic alkali, and pouring dis- 
tilled vinegar into the solution. He knew the com- 
bustibility and volatility of metallic arsenic. 

654. When we compare the knowledge possessed 
by Geber, with that of the Romans, it is evident that 
very important additions had been made to the stock 
of chemical facts. The discovery of sulphuric, ni- 
tric, and nitromuriatic acids, of arsenic, of the mer- 
curial salts, and of the solubility of sulphur in the 
alkalies, mark an era in the science, and whether or 
not they were the discoveries of Geber, entitle him 
to the epithet of the patriarch of chemistry, although 
he veiled his descriptions in the mystical jargon of 
the alchemists, so as to render them almost unin- 
telligible. 

655. From the time of Geber to the beginning of 
the twelfth century, there are few changes in the 
state of chemical knowledge of sufficient importance 
to attract attention. But the returning wave of the 
Crusades, wafted back to Europe the knowledge 
and the arts of the East, and greatly multiplied the 
number of the searchers after the Universal Medi- 



CHEMICAL PHILOSOPHY. 297 

cine, as the Philosopher's Stone was called, and the 
Elixir of Life. Too many of these were crafty im- 
postors, or their ignorant dupes, who added little to 
the stock of knowledge. A few great men, how- 
ever, appeared amid the surrounding darkness, who 
brought to light some important chemical facts. 

656. The illustrious Roger Bacon, a native of Eng- 
land, flourished in the thirteenth century. Among a 
variety of less important discoveries, he may claim 
the invention of gunpowder. "From saltpetre and 
other ingredients," says he, " we are able to form a 
fire which will burn to any distance." In another 
place he says, " a small portion of matter, about the 
size of the thumb, properly disposed, will make a 
tremendous sound and corruscation, by which cities 
and armies might be destroyed." The following 
curious passage is also found in his writings. " Sed 
tamen sales petre luru mone cap urbe, et sulphuris, 
et sic facies tonitrum si scias artificium." The 
words luru mone cap arbe, according to the fantas- 
tic fashion of the age, were an anagram of the words 
carbonum pulvere, framed to conceal his meaning 
from vulgar understandings; and there can be no 
doubt that they were designed to record, and yet to 
hide his acquaintance with the art of manufacturing 
gunpowder. 

657. In the writings of Arnold, a native of Villa 
Nova in Provence, who was born in 1235, we meet 
with the first distinct notice of spirits of wine, a 
preparation, the extraordinary effects of which on 
the human system, and its qualities as a solvent, 
rendered it an acquisition of the greatest importance 
to the empirics and pretenders of the age. 

65S. Raymond Sully, another alchemist of the 
same time, knew how to concentrate alcohol by dis- 
tillation from alkali, and he prepared the volatile 
alkali by the destructive distillation of bones, and 



298 HISTORY OF 

more particularly of the horns of the stag, which 
process is the origin of its ancient name of spirits of 
hartshorn. 

659. To Basil Valentine, in the latter part of the 
fifteenth century, we are indebted for our know- 
ledge of metallic antimony, and its principal prepa- 
rations. Paracelsus was the boldest, and the most 
famous, of all these daring innovators. He trampled 
on all authority, he united in himself all the extrav- 
agances of all his predecessors, and he awakened 
the age from its slumbers, by calling every thing in 
question, by trying every thing, and innovating in 
every thing. Yet the writings of Paracelsus do not 
add much to our stock of chemical knowledge. We 
find that zinc and bismuth were known to him, and 
he has mentioned or discovered many combinations 
and salts not before noticed. But the discovery of 
alcohol, and its powers as a menstruum, had directed 
the attention of physicians to remedies from the vege- 
table kingdom, and the alcoholic tinctures which thus 
took the place of syrups and confections, constituted 
a great advance in the science of pharmacy, although 
they added little to the list of facts in chemistry. 

660. Van Helmont, a German, who lived in the 
early part of the seventeenth century, is the first who 
appears to have suspected that there were different 
kinds of air, and who used the term gas. He knew 
that that which is given out in the fermentation of 
beer and wine, extinguished flame, and he asserted 
that it was identical with that found in the Grotto 
del Cane, near Naples. He knew that the air evolved 
during the putrefaction of animal bodies was inflam- 
mable, but it does not appear that he had noticed 
any other qualities of gases than those which relate 
to their action on flame. 

661. Glauber, a German, who lived at Amster- 
dam about the middle of the seventeenth century, 



CHEMICAL PHILOSOPHY. 299 

was one of the most industrious experimenters of 
the age. He discovered many chemical compounds 
which bear his name, and was the first who pre- 
pared chlorohydric acid, which he called spirit of 
marine salt. He obtained sulphuric acid by distil- 
ling sulphate of iron, he greatly improved the pro- 
cess for preparing nitric acid, and added many new 
instruments and apparatus to the stock already in 
use. 

662. To Brandt and Kunkel, two indefatigable 
chemists of the same age, we are indebted for the 
discovery of phosphorus. It was first obtained by 
the former, who was a chemist of Hamburg, in the 
vain attempt to extract from urine a liquid capable 
of converting silver into gold. He showed a speci- 
men to Kunkel, but refused to tell him how he ob- 
tained it. Kunkel immediately set himself to work, 
and after three or four years of labour, discovered 
the process for making it. Among the most impor- 
tant inventions of the age, was that of the thermo- 
meter, which was originally contrived by the acad- 
emicians of Florence, but was brought into notice 
by Fahrenheit, a Dutch merchant, who devoted him- 
self to the making of philosophical instruments. 

663. The close of the seventeenth, and the early 
part of the eighteenth century, are the eras of the 
foundation of chemical science. The great accumu- 
lation of facts, rendered some classification of them 
necessary, and the works of Boer, a learned Dutch 
physician, and of Lemery, an apothecary of Paris, 
the first formal treatises that have any claim to a 
philosophical spirit, were the results of this neces- 
sity. 



300 HISTORY OF 

CHAPTER III. 

THE STAHLIAN THEORY. 

664. The first attempt at a philosophical theory, 
which had any influence on the progress of the sci- 
ence, was by a German named Beecher, who furnished 
Ernest Stahl with the original ideas of the celebrated 
theory of Phlogiston. It was the genius of the latter 
which rendered this doctrine the creed of the science 
for nearly a century. He was a native of Anspach, 
and a physician of great eminence, but his chief 
merit is the attempt which he made, to explain the 
principal phenomena of chemistry by a simple and 
ingenious theory. Stahl found that the sulphurous 
and phosphoric acids, into which sulphur and phos- 
phorus were converted by burning, were reconverted 
into sulphur and phosphorus, by being heated with 
inflammable bodies. He therefore inferred that com- 
bustible bodies contain a peculiar principle of in- 
flammability, with which they part in the process of 
combustion. This principle he called phlogiston, 
and supposed that sulphur and phosphorus were 
compounds of phlogiston, with sulphurous and phos- 
phoric acids. Admitting the existence of this princi- 
ple, the proof from experiment seemed at the time 
to be complete. For all inflammable bodies are con- 
verted by combustion into substances incapable of 
being burnt, and have their inflammability restored 
by the action of another inflammable body, which 
thereby loses the property. The theory which ex- 
plained these changes, by supposing that a principle 
of inflammability had been transferred from one body 
to the other, seemed the simplest and most beautiful 
that could be devised. 

665. Unfortunately it had one fundamental error, 



CHEMICAL PHILOSOPHY. 301 

which was even in that age detected, but the detec- 
tion of which did not, in the infancy of science, 
attract the notice it deserved. If sulphur and phos- 
phorus, in burning, part with a portion of their sub- 
stance, the product of combustion should be less than 
the quantity burnt. Brun, an apothecary at Berge- 
rac, in France, melted two pounds six ounces of tin, 
and converted it into a calx, which weighed 7oz 
more than the tin employed. This experiment was 
performed as early as the year 1626, a century be- 
fore the publication of the theory of Stahl. Surprised 
at this circumstance, he communicated it to John 
Rey, a physician of Perigord, who made it the sub- 
ject of a tract published in 1 630, in which he ascribes 
the increase of the weight, to the solidification of the 
air. Had this fact presented itself in the same lights, 
to a mind as bold and comprehensive as that of 
Stahl, how much would the progress of Chemistry 
have been accelerated! for it is the key to some of 
the greatest mysteries of the science. 

That the calcination of the metals was a phenome- 
non of the same kind as the combustion of inflam- 
mable bodies, was soon perceived: for many metals 
burn with a brilliant flame when calcined at a great 
heat. The celebrated Robert Boyle attributed the 
increased weight of the burnt or calcined body, to the 
solidification of the matter of heat, with which he 
supposed the metal to have combined; but his opin- 
ion does not appear to have gained much attention. 
When the difficulty struck the phlogistic philoso- 
phers, they were driven to the necessity of supposing 
their phlogiston to possess a principle of levity, so 
that by its union with bodies it actually lessened 
their weight; and this opinion, absurd as it now 
seems, satisfied for a time the disciples of Stahl. 

666. It was the great merit of the phlogistic theory, 
that it provided a principle of classification, accord- 
ing to real distinctions in nature; the changes which 

26 



302 HISTORY OF 

bodies undergo by combustion, being in fact the foun- 
dation on which the true science of Chemistry is now 
built. The simplicity and comprehensiveness of the 
doctrine attracted numerous labourers into the vast 
field of chemical research, and the first eighty years 
of the eighteenth century were illustrated by the 
labours of men who must ever be regarded as the 
patriarchs of experimental research, and whose la- 
bours and works still retain their value. Some of 
the most illustrious of these men were Germans, 
attracted to Berlin by the fame of Stahl, and of the 
school which he there established. Scheele, Neu- 
man, Margraaf, Bergman, Klaproth, and Pott, in that 
country; Reaumur, Hellot, Macquer, Du Hamel, 
and Baume, in France; Mayow, Hales, Rutherford, 
Black, Cavendish, and Priestly, in Great Britain, 
were the most distinguished of these philosophers. 
Neuman laboured chiefly in the examination of or- 
ganic substances; Bergman and Klaproth in the anal- 
ysis of minerals. The researches of Scheele fill a large 
space in the history of Chemistry. He discovered, 
and carefully examined the properties of fluoric acid, 
in 1771; he ascertained the nature of black oxide of 
manganese, the peculiar character of baryta, the ex- 
istence of nitrogen as an element of ammonia, and 
was the first who obtained, and examined the prop- 
erties of chlorine. In conformity with the Stahlian 
theory, he called this gas dephlogisticated marine 
acid; for it was obtained from this acid by a pro- 
cess, analogous to that by which inflammable bodies 
are deprived of their plogiston. He was one of the 
discoverers of azote and oxygen; he ascertained the 
composition of prussian blue, and the properties of 
cyanhydric, or, as it was then called, the prussic 
acid. He examined the acids evolved in various 
fruits and vegetables, and his essays will bear a com- 
parison with the best productions of our own times, 
in accuracy, skill, and ingenuity. 



CHEMICAL PHILOSOPHY. 303 

667. Dr. Rutherford, of Edinburgh, discovered in 
1772, that atmospheric air which has been breathed, 
acquires new properties, and announced the exist- 
ence of a new species of air, which did not precipi- 
tate lime water, and yet was incapable of supporting 
life or combustion. The greatest advance made at 
that period, in chemical science, was due to Dr. 
Black of Edinburgh. By a series of ingenious exper- 
iments, this' philosopher, in investigating the changes 
which chalk and magnesia undergo in the fire, dis- 
covered that they lost weight, and that this loss of 
weight was occasioned, like their effervescence with 
acids, by the escape of an aeriform substance. He 
announced that chalk and magnesia consisted of a 
caustic earth, rendered mild by combination with this 
air, and which he therefore called fixed air, and 
which he afterwards proved to exist in all the mild 
alkalies. Dr. Black's greatest service to science was 
the discovery of the fact, that a quantity of heat com- 
bines with solids in becoming liquids, and with liquids 
in becoming vapours, and that it is given out by them 
when they return to their former state. He also dis- 
covered that bodies differ in the quantity of heat 
requisite to effect equal changes of temperature. 
These two capital discoveries of the nature of latent, 
and of specific caloric, may be regarded as laying the 
first sure foundations of the philosophy of heat, and 
they were demonstrated by Dr. Black in the most 
forcible and beautiful manner. 

668. The great chemical discoveries of the eight- 
eenth century, those of the nature and properties of 
oxygen gas, and of the composition of water, were 
claimed by several individuals. Scheele, in Ger- 
many, and Priestley, in England, obtained the vital 
air, as it was first called, independently of each other. 
The account which the latter gives of his discovery 
is worth recording. He had filled a glass jar with 
mercury, and inverted it in a basin of the same; 



304 HISTORY OF 

some red precipitate of quicksilver was then intro- 
duced and floated upon the quicksilver in the jar; 
heat was applied in this situation by a burning lens, 
" I presently found that air was expelled from it 
very readily. Having got three or four times as 
much as the bulk of my materials, I admitted water 
into it, and found that it was not imbibed by it. But 
what surprised me more than I can well express, 
was that a candle burned in this air with a remark- 
ably vigorous flame, very much likejthat enlarged 
flame with which a candle burns in nitrous air ex- 
posed to iron or liver of sulphur; but as I had got 
nothing like this remarkable appearance from any 
kind of air besides this peculiar modification of ni- 
trous air, and I knew no nitrous air was used in the 
preparation of mercurius calcinatus, I was utterly at 
a loss how to account for it." — Exp. and Obs. on 
different kinds of Air, &c, vol. ii. p. 107. Birming- 
ham, 1790. 

Priestley, in conformity with the doctrine of Stahl, 
supposed that this air owed its remarkable proper- 
ties as a supporter of combustion, to its being de- 
prived of phlogiston, and that the phenomenon of 
combustion was occasioned by the transfer of phlo- 
giston from the burning body to this "dephlogisti- 
cated air." We owe to Dr. Priestley the perfection 
of the pneumatic apparatus, the use of the mercu- 
rial bath, a knowledge of the properties of the pro- 
toxide and deutoxide of nitrogen, the discovery of 
chlorohydric acid gas and ammoniacal gas, besides 
a vast number of experiments and observations, that 
embraced the whole range of chemistry as it then 
extended. 

669. About the same time, Henry Cavendish, an 
English nobleman of a recluse and studious life, de- 
voted a singularly acute and patient mind to these 
researches. He was the first (a. d. 1766) who ob- 
tained hydrogen gas by the action of dilute acids 



CHEMICAL PHILOSOPHY. 305 

upon the metals, and who examined its properties. 
He also first noticed the formation of moisture, when 
this inflammable air is burned in a tube. It has been 
asserted, that the discovery of the composition of 
water is fairly to be added to the trophies which 
render the great name of James Watt illustrious; 
but the recent publication of his original manuscripts, 
prove that we owe both the first hint, and the com- 
plete demonstration of this capital discovery to Cav- 
endish. 



CHAPTER IV. 

THE LAVOISIERIAN CHEMISTRY. 

670. While the chemists of England and Ger- 
many, were thus extending the bounds of knowledge 
by the rapid accumulation of facts, a school was 
arising in France, which, guided by more profound 
and philosophical views, soon changed the aspect of 
the whole science, and laid the foundations anew in 
a juster and more skilful induction. 

Antoine Laurent Lavoisier, who is placed by com- 
mon consent at the head of these celebrated men, 
was an opulent French gentleman, who devoted the 
leisure which he could draw from the duties of a 
public station to the pursuits of science. In 1774, 
he entered the field of chemical research, in which, 
although he did -not add so many new facts to our 
stock of knowledge as some of his cotemporaries, 
he surpassed them all in comprehensive views and 
sagacious theory. The virtue and mildness of his 
private character, and the munificence with which 
he patronized science and the arts, exposed him to 
the suspicions and hatred of the madmen who rode 
upon the storm of the revolution, and he perished 

26* 



306 HISTORY OF 

on the scaffold in the prime of life. His only request 
to the officer who arrested him was, that he might 
be allowed to complete an important experimental 
investigation in which he was engaged, and it was 
heard, like the prayer of Archimedes to the Roman 
soldier, with disregard and contempt. 

671. The first great service which Lavoisier ren- 
dered to the science was his proof of the real nature 
of combustion. He demonstrated, in an extensive 
and beautiful series of experiments, that combustion 
is the union of the burning body with the vital air 
of the atmosphere, and that the calcination of the 
metals is another case of the same combination. He 
recovered the air from the bodies with which it had 
united, and showed that the weight of the product 
is in all cases equal to that of the air and of the body 
which has been consumed. He made Dr. Black's 
doctrine of latent heat the foundation of his theory 
of combustion, and contended that the heat and light 
given out in the process, are due to the latent heat 
of the vital air with which it parts in becoming 
solidified. The explanation was ingenious and plau- 
sible, and was generally received at the time, but 
subsequent researches have shown it to be insuffi- 
cient to account for their evolution in many cases of 
combustion. 

672. The researches of Lavoisier, even when not 
marked by strict originality, are masterly specimens 
of philosophical skill. It was thus that he pursued 
the investigation into the composition of water and 
of fixed air. He showed that the latter is always a 
compound of charcoal and vital air, that it is always 
produced when that substance is burned, that its 
weight is equal to that of the charcoal and the vital 
air consumed, and that it can be again converted 
into charcoal. He was the first who examined the 
nature of the change which the diamond undergoes 
when it is dissipated by exposure to an intense heat, 
and astonished the world by announcing, as the 



CHEMICAL PHILOSOPHY. 307 

startling result of his researches, the identity of dia- 
mond and charcoal. 

673. The name of Lavoisier is associated with 
that of Guyton Morveau, Berthollet, and Fourcroy, 
in the reformation of chemical nomenclature. They 
found the science overloaded with barbarous syno- 
nyms, with names either without meaning, or con- 
veying erroneous notions of the substances they de- 
signated; framed according to the caprice of the 
inventor, and embarrassing the student by the false 
impressions they created. They therefore undertook 
to frame a strictly philosophical language of chemis- 
try, every term of which should have a precise sig- 
nification, expressing, if it belonged to a simple body, 
some peculiar property, and if it were the name of 
a compound, designating the composition of the sub- 
stance. They executed this novel project with con- 
summate sagacity and success, and the beauty and 
simplicity of its new nomenclature, contributed 
greatly to render chemistry, what it soon became, 
the most popular science of the day. Even where 
their premature generalizations involved them in 
theoretical error, which vitiated the correctness of 
their language, there is no difficulty in adapting the 
nomenclature to the new discoveries without impair- 
ing its symmetry. 

G74. The details of this system have already been 
given, from which it is easy to see the errors into 
which they fell in regard to certain general- laws. 
The only acids, the composition of which was known 
to them, were those formed in the process of com- 
bustion, or proved by analysis to contain vital air. 
They therefore inferred that this air was the princi- 
ple to which all acids owed their peculiar properties, 
and they called it oxygen gas. The error consisted 
in too hasty a generalization, and long misled the 
investigations of philosophers. The first exception 
that was discovered to this rule, was by Scheele, 
who could find no oxygen in a careful analysis of 



308 HISTORY OP 

prussic acid. An error more material in its conse- 
quences was the supposed constitution of the sub- 
stance formed by the addition of oxygen gas to mu- 
riatic acid. Supposing the resulting body to be a 
compound of the two, it was inferred that the muri- 
atic acid was a combination of oxygen and an un- 
known base, which was capable of a still higher 
degree of oxygenation. This second compound was 
therefore called oxygenated, or oxymuriatic acid, 
and its supposed constitution was for many years 
unquestioned. Its properties were so peculiar, as 
reasonably to excite doubt of its being in any respect 
an acid; but these did not lead to any suspicions of 
its real nature, until, in the year 1809, Gay Lussac 
and Thenard announced that its formation was ex- 
plicable on the supposition of its being an elemen- 
tary substance. Sir Humphrey Davy, about the same 
time, subjected this body to the action of the most 
powerful decomposing agents, without its undergo- 
ing any change, and arrived at the conclusion that it 
must be regarded as a simple undecompounded 
body. On this view, muriatic acid was formed by 
the combination of hydrogen with oxymuriatic acid, 
and, when the former is converted into the latter 
by the addition of oxygen, water is always form- 
ed. These views were established by careful experi- 
ment, and strict induction, and they entirely changed 
the face of the science, and soon received a pow- 
erful confirmation by the discovery of the close- 
ly allied elements of iodine and bromine. Chemists 
no longer regarded oxygen as the sole acidifier, but 
reckoned chlorine, as the oxymuriatic acid was now 
called, iodine, bromine, sulphur, and even certain 
compound bodies, such as cyanogen, in the same 
class. 

675. To Sir Humphrey Davy we are also indebt- 
ed for the great discovery of the metallic properties 
of the bases of the alkalies and earths, and for a 
long series of successful researches in every depart- 



CHEMICAL PHILOSOPHY. 309 

ment of the science. He seized hold of the electri- 
city evolved in the voltaic circuit, and showed it to 
be the most powerful agent of decomposition that 
had hitherto been known. The researches to which 
the powers of the voltaic pile had given rise, brought 
to light the fact, that when compound bodies were 
decomposed by the electric current, acids were con- 
stantly evolved at one pole, and alkalies at the other. 
The idea was natural, that the attraction which held 
bodies together, and which was thus neutralized by 
the electrical fluids, must be the antagonist force to 
that which destroyed or suspended it, and that all 
bodies in nature are endued with resinous or with 
vitreous electricity, forces which are therefore iden- 
tical with the cause of chemical attraction. The 
most subtle and profound investigations that science 
has witnessed since the optical researches of New- 
ton, I mean those detailed in the electrical papers of 
Faraday, have given to this theory a solidity and 
an importance, which make it at the present time the 
central point of interest in the science of chemistry. 



CHAPTER V. 



THE ATOMIC THEORY. 



676. While Chemistry was thus advancing with 
rapid strides towards the point to which we have 
conducted its history, the facts had been slowly ac- 
cumulating, which became the data for the most im- 
portant generalization that had yet been attempted. 
Although Ernest Stahl had seen the necessity of 
supposing that bodies are endued with different de- 
grees of attraction, in order to explain the changes 
which take place; the law was first laid down with 
precision by Geoffroy, in 1718. "In all cases," 
says he, "where two substances which have any 



310 



HISTORY OP 



disposition to combine, are united, if there ap- 
proaches them a third, which has more affinity with 
one of the two, this one unites with the third and lets 
the other go." GeofFroy exhibited the degrees of 
this affinity, as respected the then known acids and 
bases, in the form of a table, placing that substance 
at the head of the column of affinities, which sepa- 
rated the substance whose affinities were thus given 
from all other bodies; and ranking the others in the 
order of their power of decomposition. These ta- 
bles were the result of numerous experiments, and 
formed the most valuable body of facts that had as 
yet been published in the science. 

677. In 1775, Torbern Bergman published his 
celebrated work on elective attractions, in which he 
extended and confirmed the law of GeofFroy, cor- 
rected his tables and entered into extensive investi- 
gations to ascertain the proportions in which bodies 
combine. Two years afterwards a German, named 
Wenzel, published a treatise on the doctrine of the 
affinities of bodies, which contained many accurate 
analyses. He found that when two neutral salts 
decompose each other, the resulting salts are also 
neutral, and he announced the law, that the elements 
of bodies combine in definite proportions, and that 
they combine reciprocally, so as always to neutralize 
each other. The work" of Wenzel attracted little 
attention, but Richter, in 1792, adopted the views it 
had developed, pushing the investigations further, 
and determining by analysis, the numerical quanti- 
ties of the common bases, and of the acids that would 
neutralize each other. In the mean time, 1789, an 
Irish chemist, named Higgins, had advanced the po- 
sition, that in volatile vitriolic acid, a single ultimate 
particle of sulphur is united only to a single particle 
of dephlogisticated air; and that in perfect vitriolic 
acid, every single particle of sulphur is united to two 
of dephlogisticated air, being the quantity necessary 
to saturation. 



CHEMICAL PHILOSOPHY. 311 

678. These scattered observations and uncon- 
nected researches, like the occasional notices and 
insulated experiments which preceded the Newton- 
ian era, indicated the approach of the science to- 
wards a new generalization, the full development 
of which was reserved for an illustrious Englishman. 
In 1803, John Dalton, of Manchester, turned to this 
subject the attention of a mind remarkable for its 
power of accomplishing great ends by simple means; 
for its philosophical moderation, for its acuteness 
and patience, no less than for its comprehensive 
grasp and faculty of vivid conception. In the course 
of an analysis of olefiant gas and of dicarburetted 
hydrogen, he was struck with the fact, that the carbon 
in the former was double the quantity contained in 
the latter. Reasoning from the few facts of the kind 
which readily presented themselves to his mind, he 
saw at once the real conditions of chemical combi- 
nation, and did not hesitate to proclaim the doctrine, 
that bodies combine by their ultimate particles, and 
that when more than one combination of two bodies 
exist, they must be in proportions which are multi- 
ples one of the other. 

The clearness and simplicity of the notion were 
irresistible recommendations in its favour; and he 
pursued the researches to which it led him, with an 
ardour and success that soon raised it from the rank 
of a plausible theory, to that of a profound and wide 
generalization. In 1804, he explained his theory to 
Dr. Thomas Thomson, of Edinburg, who adopted it 
in his Treatise on Chemistry, published in 1807. 
Dalton himself gave his own researches to the public 
in a short system of Chemistry printed in 1808. Dr. 
Wollaston was one of the earliest advocates of the 
new views, which he defended in a memoir on the 
super-acid and sub-acid salts, published in the year 
last mentioned. The doctrine soon became firmly 
established, over the whole chemical world, and re- 
ceived a striking confirmation from the researches of 



312 



HISTORY OP CHEMICAL PHILOSOPHY. 



Gay Lussac, who discovered that gases unite by 
volume in simple, definite, multiple proportions, and 
that the bulk of the resulting compound, when it dif- 
fers from that of its elements, always bears a simple 
definite proportion thereto. Dr. Thomson advanced 
the position that the atomic numbers of all bodies 
are exact multiples of the atomic weight of hydro- 
gen. This law, if true, would be a simplification of 
great beauty and convenience; but we are not per- 
haps able to pronounce positively on the point; for 
the unavoidable imperfections of our finest analyses, 
will always leave a slight shade of doubt around 
the numerical result of every experiment. It seems 
safer, therefore, to avoid a supposition however con- 
venient, which may lead into error, and strictly to 
abide by our experiments, leaving their verification 
and correction to more careful inquirers. 

679. The language in which Dalton expressed his 
doctrine has been much criticised. Wollaston used 
the phrase chemical equivalents. Davy chose to 
speak of chemical proportions, and others have pre- 
ferred combining numbers, as avoiding a theoretical 
and unproved assumption; but the language of Dal- 
ton has the merit of conveying clearly to the mind, 
a great and simple conception, that reaches to the 
ultimate principles of the science; and if we admit 
that the chemical atoms by which bodies combine, 
may be groups of the ultimate physical atoms, the 
doubts of the most scrupulous as to the use of his 
phraseology may be satisfied. 

The atomic theory of Dalton was the precursor of 
the still wider generalization, already alluded to, of 
Michael Faraday, and the two discoveries may be 
said to have given to the science a new impulse, 
more powerful than any which it has felt since the 
invention of the nomenclature of Lavoisier. 



THE END. 

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